<?xml version="1.0" encoding="US-ASCII"?>
<!-- DFIN New ActiveDisclosure (SM) XBRL Linkbase Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date :2023-08-03T13:50:28.6501+00:00 -->
<!-- Copyright (c) 2023 Donnelly Financial Solutions, Inc. All Rights Reserved. -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DocumentDocumentAndEntityInformation" xlink:href="algs-20230630.xsd#Role_DocumentDocumentAndEntityInformation" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquity" xlink:href="algs-20230630.xsd#StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquity" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureStockBasedCompensationTables" xlink:href="algs-20230630.xsd#Role_DisclosureStockBasedCompensationTables" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureOrganizationAdditionalInformationDetail" xlink:href="algs-20230630.xsd#Role_DisclosureOrganizationAdditionalInformationDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail" xlink:href="algs-20230630.xsd#DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosurePropertyAndEquipmentSummaryOfPropertyAndEquipmentDetail" xlink:href="algs-20230630.xsd#Role_DisclosurePropertyAndEquipmentSummaryOfPropertyAndEquipmentDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/DisclosureInvestmentsSummaryOfAvailableForSaleSecuritiesAmortizedCostGrossUnrealizedGainsLossesAndFairValueDetail" xlink:href="algs-20230630.xsd#DisclosureInvestmentsSummaryOfAvailableForSaleSecuritiesAmortizedCostGrossUnrealizedGainsLossesAndFairValueDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureInvestmentsAdditionalInformationDetail" xlink:href="algs-20230630.xsd#Role_DisclosureInvestmentsAdditionalInformationDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureLeasesAdditionalInformationDetail" xlink:href="algs-20230630.xsd#Role_DisclosureLeasesAdditionalInformationDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureDerivativeLiabilitiesAndRedeemableConvertiblePreferredStockLiabilityAdditionalInformationDetail" xlink:href="algs-20230630.xsd#Role_DisclosureDerivativeLiabilitiesAndRedeemableConvertiblePreferredStockLiabilityAdditionalInformationDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureStockBasedCompensationAdditionalInformationDetail" xlink:href="algs-20230630.xsd#Role_DisclosureStockBasedCompensationAdditionalInformationDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureStockBasedCompensationSummaryOfStockOptionsDetail" xlink:href="algs-20230630.xsd#Role_DisclosureStockBasedCompensationSummaryOfStockOptionsDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureStockBasedCompensationSummaryOfStockBasedCompensationExpenseWasAllocatedDetail" xlink:href="algs-20230630.xsd#Role_DisclosureStockBasedCompensationSummaryOfStockBasedCompensationExpenseWasAllocatedDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureFairValueSummaryOfFairValueOfFinancialInstrumentsThatAreMeasuredAtFairValueOnRecurringBasisDetail" xlink:href="algs-20230630.xsd#Role_DisclosureFairValueSummaryOfFairValueOfFinancialInstrumentsThatAreMeasuredAtFairValueOnRecurringBasisDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail" xlink:href="algs-20230630.xsd#Role_DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/DisclosureRevenueFromContractsWithCustomersAdditionalInformationDetail" xlink:href="algs-20230630.xsd#DisclosureRevenueFromContractsWithCustomersAdditionalInformationDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetail" xlink:href="algs-20230630.xsd#DisclosureIncomeTaxesAdditionalInformationDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/Role_DisclosureNetLossPerShareScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareDetail" xlink:href="algs-20230630.xsd#Role_DisclosureNetLossPerShareScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/DisclosureDiscontinuedDevelopmentOfDrugCandidatesAdditionalInformationDetail" xlink:href="algs-20230630.xsd#DisclosureDiscontinuedDevelopmentOfDrugCandidatesAdditionalInformationDetail" xlink:type="simple"/>
  <link:roleRef roleURI="http://aligos.com/20230630/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetail" xlink:href="algs-20230630.xsd#DisclosureSubsequentEventsAdditionalInformationDetail" xlink:type="simple"/>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DocumentDocumentAndEntityInformation">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentInformationLineItems" xlink:label="dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentInformationTable" xlink:label="dei_DocumentInformationTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_VotingCommonStocksMember" xlink:label="algs_VotingCommonStocksMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentType" xlink:label="dei_DocumentType"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_NonVotingCommonStocksMember" xlink:label="algs_NonVotingCommonStocksMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_AmendmentFlag" xlink:label="dei_AmendmentFlag"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentPeriodEndDate" xlink:label="dei_DocumentPeriodEndDate"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalYearFocus" xlink:label="dei_DocumentFiscalYearFocus"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="dei_DocumentFiscalPeriodFocus"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityRegistrantName" xlink:label="dei_EntityRegistrantName"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCentralIndexKey" xlink:label="dei_EntityCentralIndexKey"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCurrentReportingStatus" xlink:label="dei_EntityCurrentReportingStatus"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityInteractiveDataCurrent" xlink:label="dei_EntityInteractiveDataCurrent"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CurrentFiscalYearEndDate" xlink:label="dei_CurrentFiscalYearEndDate"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFilerCategory" xlink:label="dei_EntityFilerCategory"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="dei_EntityCommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityShellCompany" xlink:label="dei_EntityShellCompany"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntitySmallBusiness" xlink:label="dei_EntitySmallBusiness"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityEmergingGrowthCompany" xlink:label="dei_EntityEmergingGrowthCompany"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityExTransitionPeriod" xlink:label="dei_EntityExTransitionPeriod"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_Security12bTitle" xlink:label="dei_Security12bTitle"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_TradingSymbol" xlink:label="dei_TradingSymbol"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_SecurityExchangeName" xlink:label="dei_SecurityExchangeName"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFileNumber" xlink:label="dei_EntityFileNumber"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityIncorporationStateCountryCode" xlink:label="dei_EntityIncorporationStateCountryCode"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityTaxIdentificationNumber" xlink:label="dei_EntityTaxIdentificationNumber"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine1" xlink:label="dei_EntityAddressAddressLine1"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine2" xlink:label="dei_EntityAddressAddressLine2"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressCityOrTown" xlink:label="dei_EntityAddressCityOrTown"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressStateOrProvince" xlink:label="dei_EntityAddressStateOrProvince"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressPostalZipCode" xlink:label="dei_EntityAddressPostalZipCode"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CityAreaCode" xlink:label="dei_CityAreaCode"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LocalPhoneNumber" xlink:label="dei_LocalPhoneNumber"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentQuarterlyReport" xlink:label="dei_DocumentQuarterlyReport"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentTransitionReport" xlink:label="dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentInformationTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="dei_DocumentInformationTable" xlink:to="us-gaap_StatementClassOfStockAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="algs_VotingCommonStocksMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentType" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="algs_NonVotingCommonStocksMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_AmendmentFlag" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentPeriodEndDate" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentFiscalYearFocus" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentFiscalPeriodFocus" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityRegistrantName" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityCentralIndexKey" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityCurrentReportingStatus" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityInteractiveDataCurrent" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_CurrentFiscalYearEndDate" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityFilerCategory" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityCommonStockSharesOutstanding" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityShellCompany" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntitySmallBusiness" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityEmergingGrowthCompany" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="15" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityExTransitionPeriod" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="16" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_Security12bTitle" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="17" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_TradingSymbol" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="18" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_SecurityExchangeName" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="19" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityFileNumber" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="20" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityIncorporationStateCountryCode" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="21" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityTaxIdentificationNumber" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="22" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityAddressAddressLine1" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="23" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityAddressAddressLine2" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="24" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityAddressCityOrTown" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="25" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityAddressStateOrProvince" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="26" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_EntityAddressPostalZipCode" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="27" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_CityAreaCode" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="28" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_LocalPhoneNumber" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="29" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentQuarterlyReport" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="30" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_DocumentInformationLineItems" xlink:to="dei_DocumentTransitionReport" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/StatementCondensedConsolidatedStatementsOfChangesInStockholdersEquity">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="us-gaap_SeriesAPreferredStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_FollowOnOfferingMember" xlink:label="algs_FollowOnOfferingMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeriesBPreferredStockMember" xlink:label="us-gaap_SeriesBPreferredStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TemporaryEquitySharesOutstanding" xlink:label="us-gaap_TemporaryEquitySharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding" xlink:label="us-gaap_SharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationOtherLongtermIncentivePlansRequisiteServicePeriodRecognition" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationOtherLongtermIncentivePlansRequisiteServicePeriodRecognition"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationEmployeeStockPurchaseProgramRequisiteServicePeriodRecognition" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationEmployeeStockPurchaseProgramRequisiteServicePeriodRecognition"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_IssuanceOfRedeemableConvertibleStockOnExerciseOfWarrantsValue" xlink:label="algs_IssuanceOfRedeemableConvertibleStockOnExerciseOfWarrantsValue"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_IssuanceOfRedeemableConvertibleStockOnExerciseOfWarrantsShares" xlink:label="algs_IssuanceOfRedeemableConvertibleStockOnExerciseOfWarrantsShares"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedOwnshareLendingArrangementIssuanceCosts" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedOwnshareLendingArrangementIssuanceCosts"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_VestingOfEarlyExcercisedCommonStockOptionsValue" xlink:label="algs_VestingOfEarlyExcercisedCommonStockOptionsValue"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_VestingOfEarlyExercisedCommonStockOptionsFromExistingExercisesValue" xlink:label="algs_VestingOfEarlyExercisedCommonStockOptionsFromExistingExercisesValue"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_SeriesAPreferredStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_CommonStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementEquityComponentsAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquity" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="algs_FollowOnOfferingMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_SeriesBPreferredStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AdditionalPaidInCapitalMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementClassOfStockAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_TemporaryEquitySharesOutstanding" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_RetainedEarningsMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_SubsidiarySaleOfStockAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_TemporaryEquityCarryingAmountAttributableToParent" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_SharesOutstanding" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationOtherLongtermIncentivePlansRequisiteServicePeriodRecognition" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationEmployeeStockPurchaseProgramRequisiteServicePeriodRecognition" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_IssuanceOfRedeemableConvertibleStockOnExerciseOfWarrantsValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_IssuanceOfRedeemableConvertibleStockOnExerciseOfWarrantsShares" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueNewIssues" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedOwnshareLendingArrangementIssuanceCosts" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="15" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="16" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_VestingOfEarlyExcercisedCommonStockOptionsValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="17" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_VestingOfEarlyExercisedCommonStockOptionsFromExistingExercisesValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="18" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="19" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NetIncomeLoss" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureStockBasedCompensationTables">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember" xlink:label="us-gaap_RestrictedStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock" xlink:label="us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_RestrictedStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_AwardTypeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureOrganizationAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_NatureOfOperationsLineItems" xlink:label="algs_NatureOfOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_NatureOfOperationsTable" xlink:label="algs_NatureOfOperationsTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConversionOfStockNameDomain" xlink:label="us-gaap_ConversionOfStockNameDomain"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_ConversionOfStockVotingSharesMember" xlink:label="algs_ConversionOfStockVotingSharesMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityReverseStockSplit" xlink:label="us-gaap_StockholdersEquityReverseStockSplit"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConversionOfStockByUniqueDescriptionAxis" xlink:label="us-gaap_ConversionOfStockByUniqueDescriptionAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConversionOfStockNameDomain" xlink:label="us-gaap_ConversionOfStockNameDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IPOMember" xlink:label="us-gaap_IPOMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_ConversionOfStockNonVotingSharesMember" xlink:label="algs_ConversionOfStockNonVotingSharesMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OverAllotmentOptionMember" xlink:label="us-gaap_OverAllotmentOptionMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockPricePerShare" xlink:label="us-gaap_SaleOfStockPricePerShare"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction" xlink:label="us-gaap_SaleOfStockConsiderationReceivedOnTransaction"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_UnderwritingDiscountsAndCommissions" xlink:label="algs_UnderwritingDiscountsAndCommissions"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_OfferExpenses" xlink:label="algs_OfferExpenses"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConversionOfStockSharesConverted1" xlink:label="us-gaap_ConversionOfStockSharesConverted1"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsAndShortTermInvestments" xlink:label="us-gaap_CashCashEquivalentsAndShortTermInvestments"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="algs_NatureOfOperationsLineItems" xlink:to="algs_NatureOfOperationsTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ConversionOfStockNameDomain" xlink:to="algs_ConversionOfStockVotingSharesMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_NatureOfOperationsLineItems" xlink:to="us-gaap_StockholdersEquityReverseStockSplit" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="algs_NatureOfOperationsTable" xlink:to="us-gaap_SubsidiarySaleOfStockAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ConversionOfStockByUniqueDescriptionAxis" xlink:to="us-gaap_ConversionOfStockNameDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ConversionOfStockByUniqueDescriptionAxis" xlink:to="us-gaap_ConversionOfStockNameDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_IPOMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ConversionOfStockNameDomain" xlink:to="algs_ConversionOfStockNonVotingSharesMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_NatureOfOperationsLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="algs_NatureOfOperationsTable" xlink:to="us-gaap_ConversionOfStockByUniqueDescriptionAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_OverAllotmentOptionMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_NatureOfOperationsLineItems" xlink:to="us-gaap_SaleOfStockPricePerShare" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_NatureOfOperationsLineItems" xlink:to="us-gaap_SaleOfStockConsiderationReceivedOnTransaction" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_NatureOfOperationsLineItems" xlink:to="algs_UnderwritingDiscountsAndCommissions" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_NatureOfOperationsLineItems" xlink:to="algs_OfferExpenses" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_NatureOfOperationsLineItems" xlink:to="us-gaap_ConversionOfStockSharesConverted1" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_NatureOfOperationsLineItems" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_NatureOfOperationsLineItems" xlink:to="us-gaap_CashCashEquivalentsAndShortTermInvestments" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_FinancingSourcesLineItems" xlink:label="algs_FinancingSourcesLineItems"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_FinancingSourcesTable" xlink:label="algs_FinancingSourcesTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GovernmentAssistanceTypeDomain" xlink:label="us-gaap_GovernmentAssistanceTypeDomain"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_GrantByTheNationalInstituteOfHealthNihForResearchToTargetCoronavirusesMember" xlink:label="algs_GrantByTheNationalInstituteOfHealthNihForResearchToTargetCoronavirusesMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GovernmentAssistanceTypeAxis" xlink:label="us-gaap_GovernmentAssistanceTypeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GovernmentAssistanceAmount" xlink:label="us-gaap_GovernmentAssistanceAmount"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GovernmentAssistanceTypeDomain" xlink:label="us-gaap_GovernmentAssistanceTypeDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseImpairmentLoss" xlink:label="us-gaap_OperatingLeaseImpairmentLoss"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="algs_FinancingSourcesLineItems" xlink:to="algs_FinancingSourcesTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GovernmentAssistanceTypeDomain" xlink:to="algs_GrantByTheNationalInstituteOfHealthNihForResearchToTargetCoronavirusesMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="algs_FinancingSourcesTable" xlink:to="us-gaap_GovernmentAssistanceTypeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_FinancingSourcesLineItems" xlink:to="us-gaap_GovernmentAssistanceAmount" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_GovernmentAssistanceTypeAxis" xlink:to="us-gaap_GovernmentAssistanceTypeDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_GovernmentAssistanceTypeAxis" xlink:to="us-gaap_GovernmentAssistanceTypeDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_FinancingSourcesLineItems" xlink:to="us-gaap_OperatingLeaseImpairmentLoss" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosurePropertyAndEquipmentSummaryOfPropertyAndEquipmentDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="us-gaap_LeaseholdImprovementsMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquipmentMember" xlink:label="us-gaap_EquipmentMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComputerEquipmentMember" xlink:label="us-gaap_ComputerEquipmentMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FurnitureAndFixturesMember" xlink:label="us-gaap_FurnitureAndFixturesMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VehiclesMember" xlink:label="us-gaap_VehiclesMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetUnderConstructionMember" xlink:label="us-gaap_AssetUnderConstructionMember"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_PropertyPlantAndEquipmentGross" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:to="us-gaap_PropertyPlantAndEquipmentTypeDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:to="us-gaap_PropertyPlantAndEquipmentTypeDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_LeaseholdImprovementsMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:to="us-gaap_PropertyPlantAndEquipmentByTypeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_EquipmentMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_PropertyPlantAndEquipmentNet" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_ComputerEquipmentMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_FurnitureAndFixturesMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_VehiclesMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_AssetUnderConstructionMember" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/DisclosureInvestmentsSummaryOfAvailableForSaleSecuritiesAmortizedCostGrossUnrealizedGainsLossesAndFairValueDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesAmortisedCostGrossUnrealisedGainsLossesAndFairValueTable" xlink:label="algs_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesAmortisedCostGrossUnrealisedGainsLossesAndFairValueTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="us-gaap_CertificatesOfDepositMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="us-gaap_FinancialInstrumentAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="us-gaap_USTreasurySecuritiesMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="algs_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesAmortisedCostGrossUnrealisedGainsLossesAndFairValueTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="us-gaap_CertificatesOfDepositMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="algs_ScheduleOfAvailableForSaleAndHeldToMaturitySecuritiesAmortisedCostGrossUnrealisedGainsLossesAndFairValueTable" xlink:to="us-gaap_FinancialInstrumentAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="us-gaap_USTreasurySecuritiesMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecurities" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureInvestmentsAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_InvestmentInAvailableForSaleAndHeldToMaturitySecuritiesLineItems" xlink:label="algs_InvestmentInAvailableForSaleAndHeldToMaturitySecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_InvestmentInAvailableForSaleAndHeldToMaturitySecuritiesTable" xlink:label="algs_InvestmentInAvailableForSaleAndHeldToMaturitySecuritiesTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FixedMaturitiesMember" xlink:label="us-gaap_FixedMaturitiesMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestIncomeExpenseNet" xlink:label="us-gaap_InterestIncomeExpenseNet"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="algs_InvestmentInAvailableForSaleAndHeldToMaturitySecuritiesLineItems" xlink:to="algs_InvestmentInAvailableForSaleAndHeldToMaturitySecuritiesTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="algs_InvestmentInAvailableForSaleAndHeldToMaturitySecuritiesTable" xlink:to="us-gaap_InvestmentTypeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="us-gaap_FixedMaturitiesMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_InvestmentInAvailableForSaleAndHeldToMaturitySecuritiesLineItems" xlink:to="us-gaap_InterestIncomeExpenseNet" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureLeasesAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LesseeLeaseDescriptionLineItems" xlink:label="us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LesseeLeaseDescriptionTable" xlink:label="us-gaap_LesseeLeaseDescriptionTable"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_LesseeRemainingLeaseTerm" xlink:label="algs_LesseeRemainingLeaseTerm"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember_default"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_LesseeOperatingLeaseOptionToExtendTerm" xlink:label="algs_LesseeOperatingLeaseOptionToExtendTerm"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeasePayments" xlink:label="us-gaap_OperatingLeasePayments"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization" xlink:label="us-gaap_FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinanceLeaseRightOfUseAssetAccumulatedAmortization" xlink:label="us-gaap_FinanceLeaseRightOfUseAssetAccumulatedAmortization"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_LesseeLeaseDescriptionLineItems" xlink:to="us-gaap_LesseeLeaseDescriptionTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LesseeLeaseDescriptionLineItems" xlink:to="algs_LesseeRemainingLeaseTerm" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_LesseeLeaseDescriptionTable" xlink:to="srt_RangeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MinimumMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LesseeLeaseDescriptionLineItems" xlink:to="algs_LesseeOperatingLeaseOptionToExtendTerm" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LesseeLeaseDescriptionLineItems" xlink:to="us-gaap_OperatingLeasePayments" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LesseeLeaseDescriptionLineItems" xlink:to="us-gaap_FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LesseeLeaseDescriptionLineItems" xlink:to="us-gaap_FinanceLeaseRightOfUseAssetAccumulatedAmortization" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureDerivativeLiabilitiesAndRedeemableConvertiblePreferredStockLiabilityAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:label="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_DerivativeLiabilitiesAndRedeemableConvertiblePreferredStockLiabilityTable" xlink:label="algs_DerivativeLiabilitiesAndRedeemableConvertiblePreferredStockLiabilityTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="us-gaap_SeriesAPreferredStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WarrantMember" xlink:label="us-gaap_WarrantMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByLiabilityClassAxis" xlink:label="us-gaap_FairValueByLiabilityClassAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember" xlink:label="us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_PercentageOfPrincipalAmountOfNotesCoveredByWarrants" xlink:label="algs_PercentageOfPrincipalAmountOfNotesCoveredByWarrants"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_SeriesBTwoPreferredStockMember" xlink:label="algs_SeriesBTwoPreferredStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MandatorilyRedeemablePreferredStockMember" xlink:label="us-gaap_MandatorilyRedeemablePreferredStockMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_WarrantsAndRightsOutstandingMaturityPeriod" xlink:label="algs_WarrantsAndRightsOutstandingMaturityPeriod"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_WarrantsIssuedClosingDate" xlink:label="algs_WarrantsIssuedClosingDate"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_FairValueOfWarrantsUponIssuance" xlink:label="algs_FairValueOfWarrantsUponIssuance"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLiabilities" xlink:label="us-gaap_DerivativeLiabilities"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_WarrantsExercised" xlink:label="algs_WarrantsExercised"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAdjustmentOfWarrants" xlink:label="us-gaap_FairValueAdjustmentOfWarrants"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction" xlink:label="us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockPricePerShare" xlink:label="us-gaap_SaleOfStockPricePerShare"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MandatorilyRedeemablePreferredStockFairValueDisclosure" xlink:label="us-gaap_MandatorilyRedeemablePreferredStockFairValueDisclosure"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServicingLiabilityAtFairValuePeriodIncreaseDecrease" xlink:label="us-gaap_ServicingLiabilityAtFairValuePeriodIncreaseDecrease"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="algs_DerivativeLiabilitiesAndRedeemableConvertiblePreferredStockLiabilityTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="algs_DerivativeLiabilitiesAndRedeemableConvertiblePreferredStockLiabilityTable" xlink:to="srt_RangeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_SeriesAPreferredStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_WarrantMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByLiabilityClassAxis" xlink:to="us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByLiabilityClassAxis" xlink:to="us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:to="us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="algs_DerivativeLiabilitiesAndRedeemableConvertiblePreferredStockLiabilityTable" xlink:to="us-gaap_StatementClassOfStockAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="algs_PercentageOfPrincipalAmountOfNotesCoveredByWarrants" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="algs_SeriesBTwoPreferredStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MinimumMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:to="us-gaap_MandatorilyRedeemablePreferredStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="algs_DerivativeLiabilitiesAndRedeemableConvertiblePreferredStockLiabilityTable" xlink:to="us-gaap_FairValueByLiabilityClassAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="algs_WarrantsAndRightsOutstandingMaturityPeriod" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="algs_DerivativeLiabilitiesAndRedeemableConvertiblePreferredStockLiabilityTable" xlink:to="us-gaap_StatementEquityComponentsAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="algs_WarrantsIssuedClosingDate" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="algs_FairValueOfWarrantsUponIssuance" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="us-gaap_DerivativeLiabilities" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="algs_WarrantsExercised" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="us-gaap_FairValueAdjustmentOfWarrants" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="us-gaap_SaleOfStockPricePerShare" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="us-gaap_MandatorilyRedeemablePreferredStockFairValueDisclosure" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_DerivativeLiabilitiesAndConvertiblePreferredStockLiabilityLineItems" xlink:to="us-gaap_ServicingLiabilityAtFairValuePeriodIncreaseDecrease" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureStockBasedCompensationAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="us-gaap_EmployeeStockOptionMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember" xlink:label="us-gaap_RestrictedStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_EmployeeStockPurchasePlanMember" xlink:label="algs_EmployeeStockPurchasePlanMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_StockIssuesEarlyPeriodShareStockOptionsExercised" xlink:label="algs_StockIssuesEarlyPeriodShareStockOptionsExercised"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesCommonStockSubjectToRepurchaseOrCancellation" xlink:label="us-gaap_WeightedAverageNumberOfSharesCommonStockSubjectToRepurchaseOrCancellation"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_AggregatePriceForShareRepurchase" xlink:label="algs_AggregatePriceForShareRepurchase"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_EmployeeStockOptionMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_AwardTypeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_RestrictedStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="algs_EmployeeStockPurchasePlanMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="algs_StockIssuesEarlyPeriodShareStockOptionsExercised" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_WeightedAverageNumberOfSharesCommonStockSubjectToRepurchaseOrCancellation" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="algs_AggregatePriceForShareRepurchase" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureStockBasedCompensationSummaryOfStockOptionsDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="us-gaap_EmployeeStockOptionMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember" xlink:label="us-gaap_RestrictedStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueGranted" xlink:label="algs_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueGranted"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:to="us-gaap_AwardTypeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_EmployeeStockOptionMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_RestrictedStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="15" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="16" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="17" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="18" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="20" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="21" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="22" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="23" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="24" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="26" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="27" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="28" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="30" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="31" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="algs_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueGranted" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="32" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureStockBasedCompensationSummaryOfStockBasedCompensationExpenseWasAllocatedDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:to="us-gaap_IncomeStatementLocationAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_ResearchAndDevelopmentExpenseMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_GeneralAndAdministrativeExpenseMember" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureFairValueSummaryOfFairValueOfFinancialInstrumentsThatAreMeasuredAtFairValueOnRecurringBasisDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract" xlink:label="us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:label="us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="us-gaap_FairValueInputsLevel1Member"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByAssetClassAxis" xlink:label="us-gaap_FairValueByAssetClassAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="us-gaap_CertificatesOfDepositMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsFairValueDisclosure" xlink:label="us-gaap_InvestmentsFairValueDisclosure"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="us-gaap_FairValueInputsLevel2Member"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="us-gaap_USTreasurySecuritiesMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsFairValueDisclosure" xlink:label="us-gaap_AssetsFairValueDisclosure"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract" xlink:to="us-gaap_CashAndCashEquivalentsFairValueDisclosure" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel1Member" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_FairValueByAssetClassAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:to="us-gaap_CertificatesOfDepositMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByAssetClassAxis" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByAssetClassAxis" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract" xlink:to="us-gaap_InvestmentsFairValueDisclosure" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel2Member" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:to="us-gaap_USTreasurySecuritiesMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract" xlink:to="us-gaap_AssetsFairValueDisclosure" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureLicenseAndCollaborationAgreementsAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="us-gaap_SeriesAPreferredStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_EmoryUniversityMember" xlink:label="algs_EmoryUniversityMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_EmoryLicenseAgreementMember" xlink:label="algs_EmoryLicenseAgreementMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_UpfrontLicenseFeesPaid" xlink:label="algs_UpfrontLicenseFeesPaid"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_LuxnaBiotechCoLtdMember" xlink:label="algs_LuxnaBiotechCoLtdMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_LuxnaLicenseAgreementMember" xlink:label="algs_LuxnaLicenseAgreementMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_UpfrontPaymentReceived" xlink:label="algs_UpfrontPaymentReceived"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_KULeuvenMember" xlink:label="algs_KULeuvenMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_KatholiekeUniversiteitLeuvenLicenseAgreementMember" xlink:label="algs_KatholiekeUniversiteitLeuvenLicenseAgreementMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_AdditionalUpfrontPaymentReceived" xlink:label="algs_AdditionalUpfrontPaymentReceived"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_KatholiekeUniversiteitLeuvenMember" xlink:label="algs_KatholiekeUniversiteitLeuvenMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_MerckLicenseAndResearchCollaborationMember" xlink:label="algs_MerckLicenseAndResearchCollaborationMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesIssued1" xlink:label="us-gaap_NotesIssued1"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_MerckMember" xlink:label="algs_MerckMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_MerckLicenseAndResearchCollaborationFirstAmendmentMember" xlink:label="algs_MerckLicenseAndResearchCollaborationFirstAmendmentMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermPurchaseCommitmentAmount" xlink:label="us-gaap_LongTermPurchaseCommitmentAmount"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_LongTermPurchaseCommitmentAdditionalObligationToBePaid" xlink:label="algs_LongTermPurchaseCommitmentAdditionalObligationToBePaid"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCostsIncurredGross" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCostsIncurredGross"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_ResearchAndDevelopmentArrangementContractToPerformForOthersExpiryPeriod" xlink:label="algs_ResearchAndDevelopmentArrangementContractToPerformForOthersExpiryPeriod"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_ElectedExtensionTermOfCollaborationAgreement" xlink:label="algs_ElectedExtensionTermOfCollaborationAgreement"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_LongtermPurchaseCommitmentPeriodDescription" xlink:label="algs_LongtermPurchaseCommitmentPeriodDescription"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractualObligation" xlink:label="us-gaap_ContractualObligation"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_ExpenseRelatedToMilestonePayments" xlink:label="algs_ExpenseRelatedToMilestonePayments"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForRoyalties" xlink:label="us-gaap_PaymentsForRoyalties"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_ExpenseOrAccrualsRecognizedRelatedToRoyalties" xlink:label="algs_ExpenseOrAccrualsRecognizedRelatedToRoyalties"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermPurchaseCommitmentPeriod" xlink:label="us-gaap_LongtermPurchaseCommitmentPeriod"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_FirstCommercialSaleOfALicensedProductPeriod" xlink:label="algs_FirstCommercialSaleOfALicensedProductPeriod"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_MilestonePaymentsAndRoyaltiesReceivable" xlink:label="algs_MilestonePaymentsAndRoyaltiesReceivable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_ContractWithCustomerLiabilityRevenueRecognizedOnUpfrontPayment" xlink:label="algs_ContractWithCustomerLiabilityRevenueRecognizedOnUpfrontPayment"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_SeriesAPreferredStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="algs_EmoryUniversityMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" xlink:to="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" xlink:to="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:to="algs_EmoryLicenseAgreementMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_IncomeStatementLocationAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_UpfrontLicenseFeesPaid" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_ResearchAndDevelopmentExpenseMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="algs_LuxnaBiotechCoLtdMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MinimumMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:to="algs_LuxnaLicenseAgreementMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_UpfrontPaymentReceived" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="algs_KULeuvenMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:to="algs_KatholiekeUniversiteitLeuvenLicenseAgreementMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementClassOfStockAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_AdditionalUpfrontPaymentReceived" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="algs_KatholiekeUniversiteitLeuvenMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:to="algs_MerckLicenseAndResearchCollaborationMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NotesIssued1" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="algs_MerckMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:to="algs_MerckLicenseAndResearchCollaborationFirstAmendmentMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="srt_RangeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DebtInstrumentConvertibleConversionPrice1" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_LongTermPurchaseCommitmentAmount" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_LongTermPurchaseCommitmentAdditionalObligationToBePaid" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCostsIncurredGross" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_ResearchAndDevelopmentArrangementContractToPerformForOthersExpiryPeriod" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_ElectedExtensionTermOfCollaborationAgreement" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_LongtermPurchaseCommitmentPeriodDescription" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ContractualObligation" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_ExpenseRelatedToMilestonePayments" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PaymentsForRoyalties" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_ExpenseOrAccrualsRecognizedRelatedToRoyalties" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="15" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_LongtermPurchaseCommitmentPeriod" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="16" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_FirstCommercialSaleOfALicensedProductPeriod" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="17" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_MilestonePaymentsAndRoyaltiesReceivable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="18" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="19" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_ContractWithCustomerLiabilityRevenueRecognizedOnUpfrontPayment" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/DisclosureRevenueFromContractsWithCustomersAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_AmoytopMember" xlink:label="algs_AmoytopMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_AmoytopLicenseAndResearchCollaborationMember" xlink:label="algs_AmoytopLicenseAndResearchCollaborationMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_UpfrontPaymentReceived" xlink:label="algs_UpfrontPaymentReceived"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_WithholdingTaxes" xlink:label="algs_WithholdingTaxes"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_MilestonePaymentsAndRoyaltiesReceivable" xlink:label="algs_MilestonePaymentsAndRoyaltiesReceivable"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_ContractWithCustomerLiabilityDeferredRevenueRecognizedOnUpfrontPayment" xlink:label="algs_ContractWithCustomerLiabilityDeferredRevenueRecognizedOnUpfrontPayment"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="algs_AmoytopMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" xlink:to="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:to="algs_AmoytopLicenseAndResearchCollaborationMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_UpfrontPaymentReceived" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_WithholdingTaxes" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="srt_RangeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_MilestonePaymentsAndRoyaltiesReceivable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="algs_ContractWithCustomerLiabilityDeferredRevenueRecognizedOnUpfrontPayment" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_IncomeTaxesLineItems" xlink:label="algs_IncomeTaxesLineItems"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_IncomeTaxesTable" xlink:label="algs_IncomeTaxesTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_AmoytopMember" xlink:label="algs_AmoytopMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="algs_IncomeTaxesLineItems" xlink:to="algs_IncomeTaxesTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="algs_AmoytopMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="algs_IncomeTaxesTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="algs_IncomeTaxesLineItems" xlink:to="us-gaap_IncomeTaxExpenseBenefit" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/Role_DisclosureNetLossPerShareScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConvertiblePreferredStockMember" xlink:label="us-gaap_ConvertiblePreferredStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForwardContractsMember" xlink:label="us-gaap_ForwardContractsMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="us-gaap_EmployeeStockOptionMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember" xlink:label="us-gaap_RestrictedStockMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WarrantMember" xlink:label="us-gaap_WarrantMember"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="us-gaap_ConvertiblePreferredStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:to="us-gaap_AntidilutiveSecuritiesNameDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:to="us-gaap_AntidilutiveSecuritiesNameDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="us-gaap_ForwardContractsMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="us-gaap_EmployeeStockOptionMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="us-gaap_RestrictedStockMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="us-gaap_WarrantMember" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/DisclosureDiscontinuedDevelopmentOfDrugCandidatesAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationAxis" xlink:label="us-gaap_DisposalGroupClassificationAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="us-gaap_DisposalGroupClassificationDomain"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_SAntigenTransportInhibitingOligonucleotidePolymersMember" xlink:label="algs_SAntigenTransportInhibitingOligonucleotidePolymersMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="us-gaap_DisposalGroupClassificationDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PurchaseObligation" xlink:label="us-gaap_PurchaseObligation"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_AntisenseOligonucleotideMember" xlink:label="algs_AntisenseOligonucleotideMember"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:to="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:to="us-gaap_DisposalGroupClassificationAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisposalGroupClassificationDomain" xlink:to="algs_SAntigenTransportInhibitingOligonucleotidePolymersMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DisposalGroupClassificationAxis" xlink:to="us-gaap_DisposalGroupClassificationDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_DisposalGroupClassificationAxis" xlink:to="us-gaap_DisposalGroupClassificationDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:to="us-gaap_PurchaseObligation" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DisposalGroupClassificationDomain" xlink:to="algs_AntisenseOligonucleotideMember" priority="2" use="optional"/>
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://aligos.com/20230630/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventLineItems" xlink:label="us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTable" xlink:label="us-gaap_SubsequentEventTable"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain_default"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_AmoytopMember" xlink:label="algs_AmoytopMember"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_UpfrontPaymentReceived" xlink:label="algs_UpfrontPaymentReceived"/>
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember"/>
    <link:loc xlink:type="locator" xlink:href="algs-20230630.xsd#algs_MilestonePaymentsAndRoyaltiesReceivable" xlink:label="algs_MilestonePaymentsAndRoyaltiesReceivable"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_SubsequentEventTable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain_default" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="algs_AmoytopMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="algs_UpfrontPaymentReceived" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_SubsequentEventTable" xlink:to="us-gaap_SubsequentEventTypeAxis" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="algs_MilestonePaymentsAndRoyaltiesReceivable" priority="2" use="optional"/>
    <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_SubsequentEventTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" priority="2" use="optional"/>
  </link:definitionLink>
</link:linkbase>
