<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2023 Workiva-->
<!--r:65f08a08-e378-41c1-ae6e-1427f79ce66e,g:5cec771e-4778-4fc4-a658-2aed6390fb6b-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.orasure.com/role/ConsolidatedStatementsofOperations" xlink:type="simple" xlink:href="osur-20230630.xsd#ConsolidatedStatementsofOperations"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/ConsolidatedStatementsofOperations" xlink:type="extended" id="i031bb79872b04b2bba15f43f421d08f1_ConsolidatedStatementsofOperations">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_de45d22a-96da-4b63-a78e-b84fecfe68c9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:to="loc_us-gaap_RevenuesAbstract_de45d22a-96da-4b63-a78e-b84fecfe68c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_72174089-bd08-476a-8d2f-8ea2ce6efb4a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_de45d22a-96da-4b63-a78e-b84fecfe68c9" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_72174089-bd08-476a-8d2f-8ea2ce6efb4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_f1539d19-f00e-44e4-9304-47bbab35e577" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_de45d22a-96da-4b63-a78e-b84fecfe68c9" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_f1539d19-f00e-44e4-9304-47bbab35e577" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_384c9dad-d3d0-43f3-9c15-6c6ba69fc016" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_de45d22a-96da-4b63-a78e-b84fecfe68c9" xlink:to="loc_us-gaap_GrossProfit_384c9dad-d3d0-43f3-9c15-6c6ba69fc016" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_0d433e87-c5b1-487c-8dcf-9dd4ead6a178" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:to="loc_us-gaap_OperatingExpensesAbstract_0d433e87-c5b1-487c-8dcf-9dd4ead6a178" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_7c792a33-d9f9-4db4-9803-7efffc8c55db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_0d433e87-c5b1-487c-8dcf-9dd4ead6a178" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_7c792a33-d9f9-4db4-9803-7efffc8c55db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_93f1ac0e-ab46-479a-a247-cb254414e839" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingAndMarketingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_0d433e87-c5b1-487c-8dcf-9dd4ead6a178" xlink:to="loc_us-gaap_SellingAndMarketingExpense_93f1ac0e-ab46-479a-a247-cb254414e839" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_758f2f03-07f3-4a8e-b343-b82d544764fb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_0d433e87-c5b1-487c-8dcf-9dd4ead6a178" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_758f2f03-07f3-4a8e-b343-b82d544764fb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_d1cb5bb0-dfbc-47cf-b254-b6e36313e15d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_0d433e87-c5b1-487c-8dcf-9dd4ead6a178" xlink:to="loc_us-gaap_AssetImpairmentCharges_d1cb5bb0-dfbc-47cf-b254-b6e36313e15d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_69b8b95c-d31b-4933-8324-3f9efd80f708" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_0d433e87-c5b1-487c-8dcf-9dd4ead6a178" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_69b8b95c-d31b-4933-8324-3f9efd80f708" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_7b28e705-dc7b-4ffc-ba5a-a3c7afad00bc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_0d433e87-c5b1-487c-8dcf-9dd4ead6a178" xlink:to="loc_us-gaap_OperatingExpenses_7b28e705-dc7b-4ffc-ba5a-a3c7afad00bc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_6eeffb8b-83c1-452a-bab1-f353d32c4d0c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:to="loc_us-gaap_OperatingIncomeLoss_6eeffb8b-83c1-452a-bab1-f353d32c4d0c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_c361eea3-cf9f-4743-ac68-4486a2dcca02" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_c361eea3-cf9f-4743-ac68-4486a2dcca02" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_5a51610d-6b6f-4f78-b835-563896e7ef06" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_5a51610d-6b6f-4f78-b835-563896e7ef06" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_9c8a6dd2-a584-4c97-9ef1-5e423e42073e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_9c8a6dd2-a584-4c97-9ef1-5e423e42073e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_c552b040-baa9-4090-8c74-644c298258b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:to="loc_us-gaap_NetIncomeLoss_c552b040-baa9-4090-8c74-644c298258b7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_cee7830c-d2ea-4de5-8376-00ba2e4d8fdd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:to="loc_us-gaap_EarningsPerShareAbstract_cee7830c-d2ea-4de5-8376-00ba2e4d8fdd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_1a408934-943e-46d0-82d3-5f1383482009" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_cee7830c-d2ea-4de5-8376-00ba2e4d8fdd" xlink:to="loc_us-gaap_EarningsPerShareBasic_1a408934-943e-46d0-82d3-5f1383482009" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_a4e213d6-843f-40bc-88fc-15262f8c66f9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_cee7830c-d2ea-4de5-8376-00ba2e4d8fdd" xlink:to="loc_us-gaap_EarningsPerShareDiluted_a4e213d6-843f-40bc-88fc-15262f8c66f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_bb2c5191-28da-4217-a45d-f74c7613b539" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_bb2c5191-28da-4217-a45d-f74c7613b539" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_fd5a508f-32a8-4a46-b918-d8a61470a929" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_bb2c5191-28da-4217-a45d-f74c7613b539" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_fd5a508f-32a8-4a46-b918-d8a61470a929" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_eaadd246-7cd4-4b4e-b8af-593afabffacc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_bb2c5191-28da-4217-a45d-f74c7613b539" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_eaadd246-7cd4-4b4e-b8af-593afabffacc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_002c3b3a-d5bb-4f07-b495-0898a5ee96c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_25c60992-7151-4672-8c68-3d18d04e1088" xlink:to="loc_us-gaap_StatementTable_002c3b3a-d5bb-4f07-b495-0898a5ee96c2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_669d0a4a-658c-4c1c-8a47-f6d4f0f36cce" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_002c3b3a-d5bb-4f07-b495-0898a5ee96c2" xlink:to="loc_srt_ProductOrServiceAxis_669d0a4a-658c-4c1c-8a47-f6d4f0f36cce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_669d0a4a-658c-4c1c-8a47-f6d4f0f36cce_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_669d0a4a-658c-4c1c-8a47-f6d4f0f36cce" xlink:to="loc_srt_ProductsAndServicesDomain_669d0a4a-658c-4c1c-8a47-f6d4f0f36cce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_61784d22-a60e-417b-9405-a6848331d167" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_669d0a4a-658c-4c1c-8a47-f6d4f0f36cce" xlink:to="loc_srt_ProductsAndServicesDomain_61784d22-a60e-417b-9405-a6848331d167" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ProductAndServicesMember_2060013f-54cc-4827-bc76-1b3811b019f7" xlink:href="osur-20230630.xsd#osur_ProductAndServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_61784d22-a60e-417b-9405-a6848331d167" xlink:to="loc_osur_ProductAndServicesMember_2060013f-54cc-4827-bc76-1b3811b019f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_OtherRevenuesMember_a2a31e43-8dc7-48d2-bbe8-bd508411c82e" xlink:href="osur-20230630.xsd#osur_OtherRevenuesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_61784d22-a60e-417b-9405-a6848331d167" xlink:to="loc_osur_OtherRevenuesMember_a2a31e43-8dc7-48d2-bbe8-bd508411c82e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/SummaryofSignificantAccountingPoliciesSummaryofAvailableforsaleSecuritiesDetail" xlink:type="simple" xlink:href="osur-20230630.xsd#SummaryofSignificantAccountingPoliciesSummaryofAvailableforsaleSecuritiesDetail"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/SummaryofSignificantAccountingPoliciesSummaryofAvailableforsaleSecuritiesDetail" xlink:type="extended" id="i15438a1019ec47648df985de2142c03f_SummaryofSignificantAccountingPoliciesSummaryofAvailableforsaleSecuritiesDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3d5a8d81-b79d-4972-aff3-630749b61e88" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_203aba30-bee5-465f-b2f7-2c8d3da0983c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3d5a8d81-b79d-4972-aff3-630749b61e88" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_203aba30-bee5-465f-b2f7-2c8d3da0983c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_e9ec2919-81f6-4cad-b694-b4a8850a3b3f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3d5a8d81-b79d-4972-aff3-630749b61e88" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_e9ec2919-81f6-4cad-b694-b4a8850a3b3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_4f0cfaba-2d8d-47ed-8abb-94c24157fd91" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3d5a8d81-b79d-4972-aff3-630749b61e88" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_4f0cfaba-2d8d-47ed-8abb-94c24157fd91" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_307912bb-76ae-46ac-b036-ff6fe2cabfeb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3d5a8d81-b79d-4972-aff3-630749b61e88" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_307912bb-76ae-46ac-b036-ff6fe2cabfeb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_b4db7373-119a-468d-a7b7-cc554f7440b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_3d5a8d81-b79d-4972-aff3-630749b61e88" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_b4db7373-119a-468d-a7b7-cc554f7440b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_e786808d-7674-411d-8067-e58c9cbb3fad" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_b4db7373-119a-468d-a7b7-cc554f7440b7" xlink:to="loc_us-gaap_FinancialInstrumentAxis_e786808d-7674-411d-8067-e58c9cbb3fad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e786808d-7674-411d-8067-e58c9cbb3fad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e786808d-7674-411d-8067-e58c9cbb3fad" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e786808d-7674-411d-8067-e58c9cbb3fad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97cb036f-a3b5-4560-8edc-abd5641ce27e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e786808d-7674-411d-8067-e58c9cbb3fad" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97cb036f-a3b5-4560-8edc-abd5641ce27e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_GuaranteedInvestmentCertificatesMember_b5db6b9e-8124-45de-b7d3-56e7e3420299" xlink:href="osur-20230630.xsd#osur_GuaranteedInvestmentCertificatesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97cb036f-a3b5-4560-8edc-abd5641ce27e" xlink:to="loc_osur_GuaranteedInvestmentCertificatesMember_b5db6b9e-8124-45de-b7d3-56e7e3420299" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_CorporateBondsMember_d1b512db-82c6-49dc-bdc0-84683d343034" xlink:href="osur-20230630.xsd#osur_CorporateBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_97cb036f-a3b5-4560-8edc-abd5641ce27e" xlink:to="loc_osur_CorporateBondsMember_d1b512db-82c6-49dc-bdc0-84683d343034" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/SummaryofSignificantAccountingPoliciesAdditionalInformationDetail" xlink:type="simple" xlink:href="osur-20230630.xsd#SummaryofSignificantAccountingPoliciesAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/SummaryofSignificantAccountingPoliciesAdditionalInformationDetail" xlink:type="extended" id="ica6dc830e3f74d4cacef03530177275d_SummaryofSignificantAccountingPoliciesAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_90675c6a-bf3f-486a-88d2-afb417388a60" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_aaf87579-30e0-40bc-acbe-5d6eabb328c6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_90675c6a-bf3f-486a-88d2-afb417388a60" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_aaf87579-30e0-40bc-acbe-5d6eabb328c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationPlanAssets_37b86559-db07-48a6-9f2f-2a7aca9a5baf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredCompensationPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_90675c6a-bf3f-486a-88d2-afb417388a60" xlink:to="loc_us-gaap_DeferredCompensationPlanAssets_37b86559-db07-48a6-9f2f-2a7aca9a5baf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_0a725697-fdca-4358-8d48-d3c89bfbbb4c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_90675c6a-bf3f-486a-88d2-afb417388a60" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_0a725697-fdca-4358-8d48-d3c89bfbbb4c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_b3ef20ef-b783-42c5-acea-91e7d424b46d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_90675c6a-bf3f-486a-88d2-afb417388a60" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_b3ef20ef-b783-42c5-acea-91e7d424b46d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_f9a6e18d-6040-4ed5-bd18-e21b3721e734" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_90675c6a-bf3f-486a-88d2-afb417388a60" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_f9a6e18d-6040-4ed5-bd18-e21b3721e734" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_IncreaseDecreaseInCostOfProductsAndServicesSold_b200b6be-0c7c-4a42-a126-8e1835a02b8f" xlink:href="osur-20230630.xsd#osur_IncreaseDecreaseInCostOfProductsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_90675c6a-bf3f-486a-88d2-afb417388a60" xlink:to="loc_osur_IncreaseDecreaseInCostOfProductsAndServicesSold_b200b6be-0c7c-4a42-a126-8e1835a02b8f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ReimbursementOfEngineeringCost_0ab50c6e-67e4-4f22-9fd4-dabd345da642" xlink:href="osur-20230630.xsd#osur_ReimbursementOfEngineeringCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_90675c6a-bf3f-486a-88d2-afb417388a60" xlink:to="loc_osur_ReimbursementOfEngineeringCost_0ab50c6e-67e4-4f22-9fd4-dabd345da642" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_f6424cd5-95d1-4049-97e7-0cb400b2534b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_90675c6a-bf3f-486a-88d2-afb417388a60" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_f6424cd5-95d1-4049-97e7-0cb400b2534b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_758a659e-9eac-415e-8ea0-5b5e577df59c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_90675c6a-bf3f-486a-88d2-afb417388a60" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_758a659e-9eac-415e-8ea0-5b5e577df59c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_5b2f8300-466c-4f8a-bbe5-c29547fcb4c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_758a659e-9eac-415e-8ea0-5b5e577df59c" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_5b2f8300-466c-4f8a-bbe5-c29547fcb4c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_5b2f8300-466c-4f8a-bbe5-c29547fcb4c2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_5b2f8300-466c-4f8a-bbe5-c29547fcb4c2" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_5b2f8300-466c-4f8a-bbe5-c29547fcb4c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_6c7bb3bb-60e6-4730-ab5d-acb1031beb81" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_5b2f8300-466c-4f8a-bbe5-c29547fcb4c2" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_6c7bb3bb-60e6-4730-ab5d-acb1031beb81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_c4894bbc-efa9-44da-90c5-5d4619b16064" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_6c7bb3bb-60e6-4730-ab5d-acb1031beb81" xlink:to="loc_us-gaap_MoneyMarketFundsMember_c4894bbc-efa9-44da-90c5-5d4619b16064" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_GuaranteedInvestmentCertificatesMember_878971c5-8374-4259-98a0-12f091394042" xlink:href="osur-20230630.xsd#osur_GuaranteedInvestmentCertificatesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_6c7bb3bb-60e6-4730-ab5d-acb1031beb81" xlink:to="loc_osur_GuaranteedInvestmentCertificatesMember_878971c5-8374-4259-98a0-12f091394042" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_e802afb7-69e8-4705-bf2e-3c61e190bf07" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_758a659e-9eac-415e-8ea0-5b5e577df59c" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_e802afb7-69e8-4705-bf2e-3c61e190bf07" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_e802afb7-69e8-4705-bf2e-3c61e190bf07_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_e802afb7-69e8-4705-bf2e-3c61e190bf07" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_e802afb7-69e8-4705-bf2e-3c61e190bf07_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_e033307e-db9e-4be7-bc29-8d8ddd0564be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_e802afb7-69e8-4705-bf2e-3c61e190bf07" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_e033307e-db9e-4be7-bc29-8d8ddd0564be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_5269345b-400d-42e4-a82f-815945271a0c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_e033307e-db9e-4be7-bc29-8d8ddd0564be" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_5269345b-400d-42e4-a82f-815945271a0c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_d27ed1a7-055a-4a1c-b328-54998d853eac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_758a659e-9eac-415e-8ea0-5b5e577df59c" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_d27ed1a7-055a-4a1c-b328-54998d853eac" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_d27ed1a7-055a-4a1c-b328-54998d853eac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_d27ed1a7-055a-4a1c-b328-54998d853eac" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_d27ed1a7-055a-4a1c-b328-54998d853eac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_4872a113-3bfe-4933-bb29-0590dfadf78f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_d27ed1a7-055a-4a1c-b328-54998d853eac" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_4872a113-3bfe-4933-bb29-0590dfadf78f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ResearchAndDevelopmentExpensesAndOtherIncomeMember_ba3d3e83-db49-4911-8c3f-7b5388ca755b" xlink:href="osur-20230630.xsd#osur_ResearchAndDevelopmentExpensesAndOtherIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_4872a113-3bfe-4933-bb29-0590dfadf78f" xlink:to="loc_osur_ResearchAndDevelopmentExpensesAndOtherIncomeMember_ba3d3e83-db49-4911-8c3f-7b5388ca755b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_c34a5f73-17e9-4f4e-a195-e5378dcba84d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_758a659e-9eac-415e-8ea0-5b5e577df59c" xlink:to="loc_srt_ProductOrServiceAxis_c34a5f73-17e9-4f4e-a195-e5378dcba84d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_c34a5f73-17e9-4f4e-a195-e5378dcba84d_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_c34a5f73-17e9-4f4e-a195-e5378dcba84d" xlink:to="loc_srt_ProductsAndServicesDomain_c34a5f73-17e9-4f4e-a195-e5378dcba84d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_a315af93-0bc2-4586-8c8e-a87f2d072118" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_c34a5f73-17e9-4f4e-a195-e5378dcba84d" xlink:to="loc_srt_ProductsAndServicesDomain_a315af93-0bc2-4586-8c8e-a87f2d072118" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GovernmentContractMember_8bb2c12f-cf47-4b24-babe-14f87a9e746c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GovernmentContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_a315af93-0bc2-4586-8c8e-a87f2d072118" xlink:to="loc_us-gaap_GovernmentContractMember_8bb2c12f-cf47-4b24-babe-14f87a9e746c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_ddc65905-5329-4ddb-a153-840d7cab0118" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingEstimateByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_758a659e-9eac-415e-8ea0-5b5e577df59c" xlink:to="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_ddc65905-5329-4ddb-a153-840d7cab0118" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_ddc65905-5329-4ddb-a153-840d7cab0118_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingEstimateTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_ddc65905-5329-4ddb-a153-840d7cab0118" xlink:to="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_ddc65905-5329-4ddb-a153-840d7cab0118_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_64c00585-9f0d-41b1-b409-8c1268be4026" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingEstimateTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_ddc65905-5329-4ddb-a153-840d7cab0118" xlink:to="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_64c00585-9f0d-41b1-b409-8c1268be4026" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceLifeMember_585c70d5-c103-4c5c-9497-4c30c72468f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ServiceLifeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_64c00585-9f0d-41b1-b409-8c1268be4026" xlink:to="loc_us-gaap_ServiceLifeMember_585c70d5-c103-4c5c-9497-4c30c72468f5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/SummaryofSignificantAccountingPoliciesSummaryofChangesinAccumulatedOtherComprehensiveLossbyComponentDetail" xlink:type="simple" xlink:href="osur-20230630.xsd#SummaryofSignificantAccountingPoliciesSummaryofChangesinAccumulatedOtherComprehensiveLossbyComponentDetail"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/SummaryofSignificantAccountingPoliciesSummaryofChangesinAccumulatedOtherComprehensiveLossbyComponentDetail" xlink:type="extended" id="i8c65e61ffec54b9c85b46901a2946f55_SummaryofSignificantAccountingPoliciesSummaryofChangesinAccumulatedOtherComprehensiveLossbyComponentDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_01e337e8-12cd-4709-bcb6-6cf5e66ec7ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_87928d4b-7a4e-4b92-a504-0ba40b92bcd7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_01e337e8-12cd-4709-bcb6-6cf5e66ec7ce" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_87928d4b-7a4e-4b92-a504-0ba40b92bcd7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_0fe75836-95af-43df-a2cd-9156ef1519cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_87928d4b-7a4e-4b92-a504-0ba40b92bcd7" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_0fe75836-95af-43df-a2cd-9156ef1519cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_104811b5-9cf2-4cd5-8f49-9ba70db5b9e8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_87928d4b-7a4e-4b92-a504-0ba40b92bcd7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_104811b5-9cf2-4cd5-8f49-9ba70db5b9e8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_b9b82687-f10b-4b0f-993e-6a68b880169e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_540952b1-ecc7-4e0a-97ed-dfe6c3282aee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_01e337e8-12cd-4709-bcb6-6cf5e66ec7ce" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_540952b1-ecc7-4e0a-97ed-dfe6c3282aee" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_6f0b67ce-5849-4dbf-9a88-781efee2461d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_540952b1-ecc7-4e0a-97ed-dfe6c3282aee" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_6f0b67ce-5849-4dbf-9a88-781efee2461d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_6f0b67ce-5849-4dbf-9a88-781efee2461d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6f0b67ce-5849-4dbf-9a88-781efee2461d" xlink:to="loc_us-gaap_EquityComponentDomain_6f0b67ce-5849-4dbf-9a88-781efee2461d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_3e430a5a-cdbd-4d58-a57b-7687fee227c1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_6f0b67ce-5849-4dbf-9a88-781efee2461d" xlink:to="loc_us-gaap_EquityComponentDomain_3e430a5a-cdbd-4d58-a57b-7687fee227c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_005506e7-6ab7-4031-8096-0bcfa5ee6457" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3e430a5a-cdbd-4d58-a57b-7687fee227c1" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_005506e7-6ab7-4031-8096-0bcfa5ee6457" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_468e6a9a-fd43-4bd6-8233-5078d73ed37d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3e430a5a-cdbd-4d58-a57b-7687fee227c1" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_468e6a9a-fd43-4bd6-8233-5078d73ed37d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/GovernmentCapitalContractsAdditionalInformationDetails" xlink:type="simple" xlink:href="osur-20230630.xsd#GovernmentCapitalContractsAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/GovernmentCapitalContractsAdditionalInformationDetails" xlink:type="extended" id="ib53455d48d37479d86aaf0e8028dcdaf_GovernmentCapitalContractsAdditionalInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_3a33f957-e7f3-47cc-8fc4-7d9217582cf9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GovernmentContractReceivable_2ed47a54-7e9b-42ae-b444-40204eceb17a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GovernmentContractReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_3a33f957-e7f3-47cc-8fc4-7d9217582cf9" xlink:to="loc_us-gaap_GovernmentContractReceivable_2ed47a54-7e9b-42ae-b444-40204eceb17a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_PercentageWithheldUnderGovernmentContractsSubjectToValidationTesting_07338f55-1453-4cc6-8d79-3ca5555dce81" xlink:href="osur-20230630.xsd#osur_PercentageWithheldUnderGovernmentContractsSubjectToValidationTesting"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_3a33f957-e7f3-47cc-8fc4-7d9217582cf9" xlink:to="loc_osur_PercentageWithheldUnderGovernmentContractsSubjectToValidationTesting_07338f55-1453-4cc6-8d79-3ca5555dce81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ProceedsFromFundingUnderGovernmentContract_424a783b-9b89-47ef-b329-50444baf9a40" xlink:href="osur-20230630.xsd#osur_ProceedsFromFundingUnderGovernmentContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_3a33f957-e7f3-47cc-8fc4-7d9217582cf9" xlink:to="loc_osur_ProceedsFromFundingUnderGovernmentContract_424a783b-9b89-47ef-b329-50444baf9a40" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ExpectingFundAmountUnderGovernmentContract_095b3932-bab2-451e-ae97-cb9a3ff6effb" xlink:href="osur-20230630.xsd#osur_ExpectingFundAmountUnderGovernmentContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_3a33f957-e7f3-47cc-8fc4-7d9217582cf9" xlink:to="loc_osur_ExpectingFundAmountUnderGovernmentContract_095b3932-bab2-451e-ae97-cb9a3ff6effb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_45726a39-fb9a-4a65-bc50-df5813ab89e6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_3a33f957-e7f3-47cc-8fc4-7d9217582cf9" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_45726a39-fb9a-4a65-bc50-df5813ab89e6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ReimbursementOfEngineeringCost_460cfb33-3ebb-43f8-a890-adb2ad8570c6" xlink:href="osur-20230630.xsd#osur_ReimbursementOfEngineeringCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_3a33f957-e7f3-47cc-8fc4-7d9217582cf9" xlink:to="loc_osur_ReimbursementOfEngineeringCost_460cfb33-3ebb-43f8-a890-adb2ad8570c6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_2b46c26b-fa9c-4b97-9a75-c7e1a426a696" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_3a33f957-e7f3-47cc-8fc4-7d9217582cf9" xlink:to="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_2b46c26b-fa9c-4b97-9a75-c7e1a426a696" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_325df80e-19e9-41b6-b95e-92f624c0ecbe" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_2b46c26b-fa9c-4b97-9a75-c7e1a426a696" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_325df80e-19e9-41b6-b95e-92f624c0ecbe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_325df80e-19e9-41b6-b95e-92f624c0ecbe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_325df80e-19e9-41b6-b95e-92f624c0ecbe" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_325df80e-19e9-41b6-b95e-92f624c0ecbe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_9c45ff99-4a31-4b7b-b6da-be391e8b9abd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_325df80e-19e9-41b6-b95e-92f624c0ecbe" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_9c45ff99-4a31-4b7b-b6da-be391e8b9abd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ResearchAndDevelopmentExpensesAndOtherIncomeMember_8edd00f1-f1ef-40d7-a75c-18d6316e270b" xlink:href="osur-20230630.xsd#osur_ResearchAndDevelopmentExpensesAndOtherIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_9c45ff99-4a31-4b7b-b6da-be391e8b9abd" xlink:to="loc_osur_ResearchAndDevelopmentExpensesAndOtherIncomeMember_8edd00f1-f1ef-40d7-a75c-18d6316e270b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIncomeMember_9995d098-3953-44b8-818c-a4b33631d2fb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_9c45ff99-4a31-4b7b-b6da-be391e8b9abd" xlink:to="loc_us-gaap_OtherIncomeMember_9995d098-3953-44b8-818c-a4b33631d2fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_f6b4ea63-9300-459d-b940-187ac8438266" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_2b46c26b-fa9c-4b97-9a75-c7e1a426a696" xlink:to="loc_srt_ProductOrServiceAxis_f6b4ea63-9300-459d-b940-187ac8438266" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_f6b4ea63-9300-459d-b940-187ac8438266_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_f6b4ea63-9300-459d-b940-187ac8438266" xlink:to="loc_srt_ProductsAndServicesDomain_f6b4ea63-9300-459d-b940-187ac8438266_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_723315f3-b484-457a-88a4-f64696caa82b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_f6b4ea63-9300-459d-b940-187ac8438266" xlink:to="loc_srt_ProductsAndServicesDomain_723315f3-b484-457a-88a4-f64696caa82b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GovernmentContractMember_e6655a8c-9417-490c-91ad-1bf109246142" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GovernmentContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_723315f3-b484-457a-88a4-f64696caa82b" xlink:to="loc_us-gaap_GovernmentContractMember_e6655a8c-9417-490c-91ad-1bf109246142" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/GovernmentCapitalContractsSummaryofGovernmentContractsBalancesIncludedinConsolidatedBalanceSheetDetails" xlink:type="simple" xlink:href="osur-20230630.xsd#GovernmentCapitalContractsSummaryofGovernmentContractsBalancesIncludedinConsolidatedBalanceSheetDetails"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/GovernmentCapitalContractsSummaryofGovernmentContractsBalancesIncludedinConsolidatedBalanceSheetDetails" xlink:type="extended" id="if2eb295f939e49e0a3086c27dbd5c50a_GovernmentCapitalContractsSummaryofGovernmentContractsBalancesIncludedinConsolidatedBalanceSheetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_ef707afc-f94d-46ba-b2f5-9ebe8736ee0f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrentAbstract_2535e883-79be-4053-9520-deab94cb1a67" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_ef707afc-f94d-46ba-b2f5-9ebe8736ee0f" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrentAbstract_2535e883-79be-4053-9520-deab94cb1a67" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BilledContractReceivables_7f8a84de-4f27-4ddc-8b93-c8fdf548e41b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BilledContractReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrentAbstract_2535e883-79be-4053-9520-deab94cb1a67" xlink:to="loc_us-gaap_BilledContractReceivables_7f8a84de-4f27-4ddc-8b93-c8fdf548e41b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnbilledContractsReceivable_6669aa59-a99b-4283-8f42-67776c2c49da" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnbilledContractsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrentAbstract_2535e883-79be-4053-9520-deab94cb1a67" xlink:to="loc_us-gaap_UnbilledContractsReceivable_6669aa59-a99b-4283-8f42-67776c2c49da" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_5120f1dc-bd06-4007-89f0-79bf5a87a1a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrentAbstract_2535e883-79be-4053-9520-deab94cb1a67" xlink:to="loc_us-gaap_OtherAssetsCurrent_5120f1dc-bd06-4007-89f0-79bf5a87a1a7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_AccruedExpensesAndOtherCurrentLiabilities_ac1236e1-7671-4ef0-869f-2ca1a6135ab7" xlink:href="osur-20230630.xsd#osur_AccruedExpensesAndOtherCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_ef707afc-f94d-46ba-b2f5-9ebe8736ee0f" xlink:to="loc_osur_AccruedExpensesAndOtherCurrentLiabilities_ac1236e1-7671-4ef0-869f-2ca1a6135ab7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_933fd52b-67b2-4898-9d4c-8b53a76f0eb6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_ef707afc-f94d-46ba-b2f5-9ebe8736ee0f" xlink:to="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_933fd52b-67b2-4898-9d4c-8b53a76f0eb6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_fd99fa72-29c3-4207-bfaa-49cb9b391191" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_933fd52b-67b2-4898-9d4c-8b53a76f0eb6" xlink:to="loc_srt_ProductOrServiceAxis_fd99fa72-29c3-4207-bfaa-49cb9b391191" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_fd99fa72-29c3-4207-bfaa-49cb9b391191_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_fd99fa72-29c3-4207-bfaa-49cb9b391191" xlink:to="loc_srt_ProductsAndServicesDomain_fd99fa72-29c3-4207-bfaa-49cb9b391191_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_114a89ed-3d47-4fd2-85af-543376d02901" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_fd99fa72-29c3-4207-bfaa-49cb9b391191" xlink:to="loc_srt_ProductsAndServicesDomain_114a89ed-3d47-4fd2-85af-543376d02901" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GovernmentContractMember_7f3e8d07-4fb2-4758-b840-3daa950359c4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GovernmentContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_114a89ed-3d47-4fd2-85af-543376d02901" xlink:to="loc_us-gaap_GovernmentContractMember_7f3e8d07-4fb2-4758-b840-3daa950359c4" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/GovernmentCapitalContractsSummaryofGovernmentContractsBalancesIncludedinConsolidatedStatementsofCashflowsDetail" xlink:type="simple" xlink:href="osur-20230630.xsd#GovernmentCapitalContractsSummaryofGovernmentContractsBalancesIncludedinConsolidatedStatementsofCashflowsDetail"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/GovernmentCapitalContractsSummaryofGovernmentContractsBalancesIncludedinConsolidatedStatementsofCashflowsDetail" xlink:type="extended" id="i4c5dbcdf31e24859aa2048500a10a5e1_GovernmentCapitalContractsSummaryofGovernmentContractsBalancesIncludedinConsolidatedStatementsofCashflowsDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_b8ec4a2e-3837-48a7-8f2d-e02c340dfb43" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_bcd7892f-0b7c-400e-a679-9421d21ef200" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_b8ec4a2e-3837-48a7-8f2d-e02c340dfb43" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_bcd7892f-0b7c-400e-a679-9421d21ef200" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_FundingEarnedNotYetReceived_37108577-b224-4eb9-a375-8bccca1a10df" xlink:href="osur-20230630.xsd#osur_FundingEarnedNotYetReceived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_b8ec4a2e-3837-48a7-8f2d-e02c340dfb43" xlink:to="loc_osur_FundingEarnedNotYetReceived_37108577-b224-4eb9-a375-8bccca1a10df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_FundingReceivedAmount_e3db84b3-8312-4d5e-8228-915b926c1a3e" xlink:href="osur-20230630.xsd#osur_FundingReceivedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_b8ec4a2e-3837-48a7-8f2d-e02c340dfb43" xlink:to="loc_osur_FundingReceivedAmount_e3db84b3-8312-4d5e-8228-915b926c1a3e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_4e6536b7-2d0d-4482-b006-e7ca4083eebb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_b8ec4a2e-3837-48a7-8f2d-e02c340dfb43" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_4e6536b7-2d0d-4482-b006-e7ca4083eebb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_29e13e58-25d1-4550-92da-6b90719017d2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_b8ec4a2e-3837-48a7-8f2d-e02c340dfb43" xlink:to="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_29e13e58-25d1-4550-92da-6b90719017d2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_f3f7f9ab-835f-476a-a578-07130f28d831" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_29e13e58-25d1-4550-92da-6b90719017d2" xlink:to="loc_srt_ProductOrServiceAxis_f3f7f9ab-835f-476a-a578-07130f28d831" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_f3f7f9ab-835f-476a-a578-07130f28d831_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_f3f7f9ab-835f-476a-a578-07130f28d831" xlink:to="loc_srt_ProductsAndServicesDomain_f3f7f9ab-835f-476a-a578-07130f28d831_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_8297f97d-2cb3-4f47-8421-6892635e2df1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_f3f7f9ab-835f-476a-a578-07130f28d831" xlink:to="loc_srt_ProductsAndServicesDomain_8297f97d-2cb3-4f47-8421-6892635e2df1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GovernmentContractMember_1a220964-0842-4193-a1b6-7f9f9a0a15fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GovernmentContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_8297f97d-2cb3-4f47-8421-6892635e2df1" xlink:to="loc_us-gaap_GovernmentContractMember_1a220964-0842-4193-a1b6-7f9f9a0a15fd" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/PropertyPlantandEquipmentNetScheduleofPropertyPlantandEquipmentDetail" xlink:type="simple" xlink:href="osur-20230630.xsd#PropertyPlantandEquipmentNetScheduleofPropertyPlantandEquipmentDetail"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/PropertyPlantandEquipmentNetScheduleofPropertyPlantandEquipmentDetail" xlink:type="extended" id="if16ddd82ed2347df9be0cb13a93c5a1c_PropertyPlantandEquipmentNetScheduleofPropertyPlantandEquipmentDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8d3a02f2-3d35-437c-b519-bdd5e972018a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_a28e7c8a-e2a0-403b-affe-d6c00e417af2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8d3a02f2-3d35-437c-b519-bdd5e972018a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_a28e7c8a-e2a0-403b-affe-d6c00e417af2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_a106f3a7-5e58-4ec0-aa31-82caf0d9210c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8d3a02f2-3d35-437c-b519-bdd5e972018a" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_a106f3a7-5e58-4ec0-aa31-82caf0d9210c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_40674fde-69bd-4309-89ef-91941b0ef96e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8d3a02f2-3d35-437c-b519-bdd5e972018a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_40674fde-69bd-4309-89ef-91941b0ef96e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_d37dc1c8-a0dc-4ee3-8d26-34bc6d0b7e45" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_8d3a02f2-3d35-437c-b519-bdd5e972018a" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_d37dc1c8-a0dc-4ee3-8d26-34bc6d0b7e45" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_54f0189c-3623-4c2b-aa4f-1684859ad868" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_d37dc1c8-a0dc-4ee3-8d26-34bc6d0b7e45" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_54f0189c-3623-4c2b-aa4f-1684859ad868" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_54f0189c-3623-4c2b-aa4f-1684859ad868_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_54f0189c-3623-4c2b-aa4f-1684859ad868" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_54f0189c-3623-4c2b-aa4f-1684859ad868_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_50b9112e-c623-4181-8a2f-4c3ee7d5d834" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_54f0189c-3623-4c2b-aa4f-1684859ad868" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_50b9112e-c623-4181-8a2f-4c3ee7d5d834" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandMember_d5d6fd00-d98f-48f3-9712-d6c153d00efd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_50b9112e-c623-4181-8a2f-4c3ee7d5d834" xlink:to="loc_us-gaap_LandMember_d5d6fd00-d98f-48f3-9712-d6c153d00efd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingAndBuildingImprovementsMember_27be532c-30b7-40ea-a196-9672568a19ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BuildingAndBuildingImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_50b9112e-c623-4181-8a2f-4c3ee7d5d834" xlink:to="loc_us-gaap_BuildingAndBuildingImprovementsMember_27be532c-30b7-40ea-a196-9672568a19ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MachineryAndEquipmentMember_b9500639-5b10-400f-8615-3f44c2a1b0c1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MachineryAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_50b9112e-c623-4181-8a2f-4c3ee7d5d834" xlink:to="loc_us-gaap_MachineryAndEquipmentMember_b9500639-5b10-400f-8615-3f44c2a1b0c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ComputerEquipmentAndSoftwareMember_e3395684-bd4b-4c21-9cb9-07ce256102f8" xlink:href="osur-20230630.xsd#osur_ComputerEquipmentAndSoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_50b9112e-c623-4181-8a2f-4c3ee7d5d834" xlink:to="loc_osur_ComputerEquipmentAndSoftwareMember_e3395684-bd4b-4c21-9cb9-07ce256102f8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_a4eb4b99-95e4-4e1f-a214-87611570285c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_50b9112e-c623-4181-8a2f-4c3ee7d5d834" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_a4eb4b99-95e4-4e1f-a214-87611570285c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_256f164f-2068-4dce-9ef4-a8568251576d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_50b9112e-c623-4181-8a2f-4c3ee7d5d834" xlink:to="loc_us-gaap_ConstructionInProgressMember_256f164f-2068-4dce-9ef4-a8568251576d" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/TerminationBenefitsSummaryofOneTimeTerminationBenefitsDetails" xlink:type="simple" xlink:href="osur-20230630.xsd#TerminationBenefitsSummaryofOneTimeTerminationBenefitsDetails"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/TerminationBenefitsSummaryofOneTimeTerminationBenefitsDetails" xlink:type="extended" id="ic8ea98ce7d39400cbd4db4707aba32bc_TerminationBenefitsSummaryofOneTimeTerminationBenefitsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_osur_TerminationBenefitsLineItems_3ee53fe7-7234-48b9-9c09-cb4a12a1269c" xlink:href="osur-20230630.xsd#osur_TerminationBenefitsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_TerminationBenefits_e55ef8c7-e64b-446b-869c-c90d0c5b2e1f" xlink:href="osur-20230630.xsd#osur_TerminationBenefits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_osur_TerminationBenefitsLineItems_3ee53fe7-7234-48b9-9c09-cb4a12a1269c" xlink:to="loc_osur_TerminationBenefits_e55ef8c7-e64b-446b-869c-c90d0c5b2e1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_TerminationBenefitsTable_e81d15fa-88d3-4c3d-9769-e1ee5ad86ec2" xlink:href="osur-20230630.xsd#osur_TerminationBenefitsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_osur_TerminationBenefitsLineItems_3ee53fe7-7234-48b9-9c09-cb4a12a1269c" xlink:to="loc_osur_TerminationBenefitsTable_e81d15fa-88d3-4c3d-9769-e1ee5ad86ec2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_d77893c5-12e5-403a-8c7e-ef270d26bb22" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_osur_TerminationBenefitsTable_e81d15fa-88d3-4c3d-9769-e1ee5ad86ec2" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_d77893c5-12e5-403a-8c7e-ef270d26bb22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_d77893c5-12e5-403a-8c7e-ef270d26bb22_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_d77893c5-12e5-403a-8c7e-ef270d26bb22" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_d77893c5-12e5-403a-8c7e-ef270d26bb22_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_69100969-756f-44cf-aebd-70a9f70bc6b6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_d77893c5-12e5-403a-8c7e-ef270d26bb22" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_69100969-756f-44cf-aebd-70a9f70bc6b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OneTimeTerminationBenefitsMember_9874c6a3-e2f3-4637-98f6-be8451283565" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OneTimeTerminationBenefitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_69100969-756f-44cf-aebd-70a9f70bc6b6" xlink:to="loc_us-gaap_OneTimeTerminationBenefitsMember_9874c6a3-e2f3-4637-98f6-be8451283565" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_3e517a34-874d-4657-898a-92f9ca44fb0d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_osur_TerminationBenefitsTable_e81d15fa-88d3-4c3d-9769-e1ee5ad86ec2" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_3e517a34-874d-4657-898a-92f9ca44fb0d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_3e517a34-874d-4657-898a-92f9ca44fb0d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_3e517a34-874d-4657-898a-92f9ca44fb0d" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_3e517a34-874d-4657-898a-92f9ca44fb0d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_fb3d338c-5a7c-4177-a393-b013b07d0fd7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_3e517a34-874d-4657-898a-92f9ca44fb0d" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_fb3d338c-5a7c-4177-a393-b013b07d0fd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_b87a55ce-999a-4fb9-a7e5-be0c389b9006" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_fb3d338c-5a7c-4177-a393-b013b07d0fd7" xlink:to="loc_us-gaap_CostOfSalesMember_b87a55ce-999a-4fb9-a7e5-be0c389b9006" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_755a418c-6b3c-421a-baaa-df4d66447422" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_fb3d338c-5a7c-4177-a393-b013b07d0fd7" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_755a418c-6b3c-421a-baaa-df4d66447422" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_1a89c77c-2ba1-4b4c-9e42-f3e87abea5e2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingAndMarketingExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_fb3d338c-5a7c-4177-a393-b013b07d0fd7" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_1a89c77c-2ba1-4b4c-9e42-f3e87abea5e2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_ee7dc9ec-cdf7-4ce5-bbd4-f4218fc76b3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_fb3d338c-5a7c-4177-a393-b013b07d0fd7" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_ee7dc9ec-cdf7-4ce5-bbd4-f4218fc76b3e" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/RevenuesSummaryofTotalNetRevenuesbyProductLineDetail" xlink:type="simple" xlink:href="osur-20230630.xsd#RevenuesSummaryofTotalNetRevenuesbyProductLineDetail"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/RevenuesSummaryofTotalNetRevenuesbyProductLineDetail" xlink:type="extended" id="i731406f64fc946b9bffff9eece6d6c32_RevenuesSummaryofTotalNetRevenuesbyProductLineDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_c534b52d-7e61-40a9-be5f-72ac8711e36f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d5634a0b-895f-4cdf-a0c8-ad45bac03060" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_c534b52d-7e61-40a9-be5f-72ac8711e36f" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d5634a0b-895f-4cdf-a0c8-ad45bac03060" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_5cc3b748-f262-470f-8281-684f44d05b7b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_c534b52d-7e61-40a9-be5f-72ac8711e36f" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_5cc3b748-f262-470f-8281-684f44d05b7b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_429bc1f5-30c9-4417-8690-cfcb2f696b9b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_5cc3b748-f262-470f-8281-684f44d05b7b" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_429bc1f5-30c9-4417-8690-cfcb2f696b9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_429bc1f5-30c9-4417-8690-cfcb2f696b9b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_429bc1f5-30c9-4417-8690-cfcb2f696b9b" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_429bc1f5-30c9-4417-8690-cfcb2f696b9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_40d78cf4-bb62-4b40-bad7-8603d5f81148" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_429bc1f5-30c9-4417-8690-cfcb2f696b9b" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_40d78cf4-bb62-4b40-bad7-8603d5f81148" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesMember_6c1eac55-e21b-4691-98c5-eab6ee5c22c3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_40d78cf4-bb62-4b40-bad7-8603d5f81148" xlink:to="loc_us-gaap_SalesMember_6c1eac55-e21b-4691-98c5-eab6ee5c22c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIncomeMember_8491021c-0f96-491e-ac34-bbabb79f46cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_40d78cf4-bb62-4b40-bad7-8603d5f81148" xlink:to="loc_us-gaap_OtherIncomeMember_8491021c-0f96-491e-ac34-bbabb79f46cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_91d49cd4-ec5c-4d6d-8583-fbc003cd3f52" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_5cc3b748-f262-470f-8281-684f44d05b7b" xlink:to="loc_srt_ProductOrServiceAxis_91d49cd4-ec5c-4d6d-8583-fbc003cd3f52" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_91d49cd4-ec5c-4d6d-8583-fbc003cd3f52_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_91d49cd4-ec5c-4d6d-8583-fbc003cd3f52" xlink:to="loc_srt_ProductsAndServicesDomain_91d49cd4-ec5c-4d6d-8583-fbc003cd3f52_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_0a9a8122-9244-438a-9fa3-338f2e8b4dd4" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_91d49cd4-ec5c-4d6d-8583-fbc003cd3f52" xlink:to="loc_srt_ProductsAndServicesDomain_0a9a8122-9244-438a-9fa3-338f2e8b4dd4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_COVID19Member_f0d69e1e-649c-4a34-a1bd-f2df67371bdd" xlink:href="osur-20230630.xsd#osur_COVID19Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0a9a8122-9244-438a-9fa3-338f2e8b4dd4" xlink:to="loc_osur_COVID19Member_f0d69e1e-649c-4a34-a1bd-f2df67371bdd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_HivMember_16aaa09e-5845-4ca5-b86e-2da565d7f9d8" xlink:href="osur-20230630.xsd#osur_HivMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0a9a8122-9244-438a-9fa3-338f2e8b4dd4" xlink:to="loc_osur_HivMember_16aaa09e-5845-4ca5-b86e-2da565d7f9d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_MolecularProductsMember_fa956d15-59a6-474e-b673-8194594ca845" xlink:href="osur-20230630.xsd#osur_MolecularProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0a9a8122-9244-438a-9fa3-338f2e8b4dd4" xlink:to="loc_osur_MolecularProductsMember_fa956d15-59a6-474e-b673-8194594ca845" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_HcvMember_051c35bc-c782-4246-9162-8c68ed2ecc6a" xlink:href="osur-20230630.xsd#osur_HcvMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0a9a8122-9244-438a-9fa3-338f2e8b4dd4" xlink:to="loc_osur_HcvMember_051c35bc-c782-4246-9162-8c68ed2ecc6a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_RiskAssessmentTestingMember_7c49b09f-4f33-4af0-a15a-a400bede0af5" xlink:href="osur-20230630.xsd#osur_RiskAssessmentTestingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0a9a8122-9244-438a-9fa3-338f2e8b4dd4" xlink:to="loc_osur_RiskAssessmentTestingMember_7c49b09f-4f33-4af0-a15a-a400bede0af5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_MolecularServicesMember_4f37136a-6cf2-42a0-a8ab-cf94865a7c8c" xlink:href="osur-20230630.xsd#osur_MolecularServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0a9a8122-9244-438a-9fa3-338f2e8b4dd4" xlink:to="loc_osur_MolecularServicesMember_4f37136a-6cf2-42a0-a8ab-cf94865a7c8c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_OtherProductAndServicesRevenuesMember_d294f3ee-773d-45d6-89df-095379a22416" xlink:href="osur-20230630.xsd#osur_OtherProductAndServicesRevenuesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0a9a8122-9244-438a-9fa3-338f2e8b4dd4" xlink:to="loc_osur_OtherProductAndServicesRevenuesMember_d294f3ee-773d-45d6-89df-095379a22416" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_OtherNonProductRevenuesMember_913627d0-0dd4-40da-bc9c-76cf5b7c484e" xlink:href="osur-20230630.xsd#osur_OtherNonProductRevenuesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0a9a8122-9244-438a-9fa3-338f2e8b4dd4" xlink:to="loc_osur_OtherNonProductRevenuesMember_913627d0-0dd4-40da-bc9c-76cf5b7c484e" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/RevenuesSummaryofTotalNetRevenuesbyGeographicAreaDetail" xlink:type="simple" xlink:href="osur-20230630.xsd#RevenuesSummaryofTotalNetRevenuesbyGeographicAreaDetail"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/RevenuesSummaryofTotalNetRevenuesbyGeographicAreaDetail" xlink:type="extended" id="i339da53a79fe41ebbef17fe364f459f3_RevenuesSummaryofTotalNetRevenuesbyGeographicAreaDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_754e3a03-3d91-45da-832d-f7c8770bd941" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_1821e02f-061b-4f5b-8bd8-ed7539173451" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_754e3a03-3d91-45da-832d-f7c8770bd941" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_1821e02f-061b-4f5b-8bd8-ed7539173451" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_24b21e60-e6e9-47af-a02d-8ae614aed67d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_754e3a03-3d91-45da-832d-f7c8770bd941" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_24b21e60-e6e9-47af-a02d-8ae614aed67d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_24cd5da3-c4bb-41b5-a9bb-627bccbb8f38" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_24b21e60-e6e9-47af-a02d-8ae614aed67d" xlink:to="loc_srt_StatementGeographicalAxis_24cd5da3-c4bb-41b5-a9bb-627bccbb8f38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_24cd5da3-c4bb-41b5-a9bb-627bccbb8f38_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_24cd5da3-c4bb-41b5-a9bb-627bccbb8f38" xlink:to="loc_srt_SegmentGeographicalDomain_24cd5da3-c4bb-41b5-a9bb-627bccbb8f38_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_beb6727a-2a78-4a15-8a37-b48416a32bbe" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_24cd5da3-c4bb-41b5-a9bb-627bccbb8f38" xlink:to="loc_srt_SegmentGeographicalDomain_beb6727a-2a78-4a15-8a37-b48416a32bbe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_671647ed-411e-43d2-8e30-368b07870f32" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_beb6727a-2a78-4a15-8a37-b48416a32bbe" xlink:to="loc_country_US_671647ed-411e-43d2-8e30-368b07870f32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EuropeMember_4ffc2b81-c397-4111-ab30-f7c4eedfa7d3" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_EuropeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_beb6727a-2a78-4a15-8a37-b48416a32bbe" xlink:to="loc_srt_EuropeMember_4ffc2b81-c397-4111-ab30-f7c4eedfa7d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_OtherForeignCountriesMember_6d7ac947-7fd8-4ed7-b4d7-37a287f1b22e" xlink:href="osur-20230630.xsd#osur_OtherForeignCountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_beb6727a-2a78-4a15-8a37-b48416a32bbe" xlink:to="loc_osur_OtherForeignCountriesMember_6d7ac947-7fd8-4ed7-b4d7-37a287f1b22e" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/RevenuesAdditionalInformationDetail" xlink:type="simple" xlink:href="osur-20230630.xsd#RevenuesAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/RevenuesAdditionalInformationDetail" xlink:type="extended" id="ia243d161a3684690978f56c7e13d7f8a_RevenuesAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:label="loc_osur_RevenueFromContractWithCustomerLineItems_c04266c4-9e04-4bad-9935-4fc58677076e" xlink:href="osur-20230630.xsd#osur_RevenueFromContractWithCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ConcentrationRiskNumberOfCustomers_7a7d9fa7-432d-4381-bbb1-04f7e821a8e8" xlink:href="osur-20230630.xsd#osur_ConcentrationRiskNumberOfCustomers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_osur_RevenueFromContractWithCustomerLineItems_c04266c4-9e04-4bad-9935-4fc58677076e" xlink:to="loc_osur_ConcentrationRiskNumberOfCustomers_7a7d9fa7-432d-4381-bbb1-04f7e821a8e8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_e68ed453-121e-4028-8ac3-c44c2652c27c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_osur_RevenueFromContractWithCustomerLineItems_c04266c4-9e04-4bad-9935-4fc58677076e" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_e68ed453-121e-4028-8ac3-c44c2652c27c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_2072d430-5318-428b-b852-fbf199d17754" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_osur_RevenueFromContractWithCustomerLineItems_c04266c4-9e04-4bad-9935-4fc58677076e" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_2072d430-5318-428b-b852-fbf199d17754" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_RevenueFromContractWithCustomerTable_6fcb35df-ed8d-49bf-aad2-7a0aa3f5fac3" xlink:href="osur-20230630.xsd#osur_RevenueFromContractWithCustomerTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_osur_RevenueFromContractWithCustomerLineItems_c04266c4-9e04-4bad-9935-4fc58677076e" xlink:to="loc_osur_RevenueFromContractWithCustomerTable_6fcb35df-ed8d-49bf-aad2-7a0aa3f5fac3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_906d321e-9a0e-4fd5-ae0b-daafc39e186d" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_osur_RevenueFromContractWithCustomerTable_6fcb35df-ed8d-49bf-aad2-7a0aa3f5fac3" xlink:to="loc_srt_MajorCustomersAxis_906d321e-9a0e-4fd5-ae0b-daafc39e186d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_906d321e-9a0e-4fd5-ae0b-daafc39e186d_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_906d321e-9a0e-4fd5-ae0b-daafc39e186d" xlink:to="loc_srt_NameOfMajorCustomerDomain_906d321e-9a0e-4fd5-ae0b-daafc39e186d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_2dd75be4-fcbe-4736-a4d2-bca197694277" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_906d321e-9a0e-4fd5-ae0b-daafc39e186d" xlink:to="loc_srt_NameOfMajorCustomerDomain_2dd75be4-fcbe-4736-a4d2-bca197694277" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_CustomerOneMember_475da378-4821-450f-9457-474c5d032c8b" xlink:href="osur-20230630.xsd#osur_CustomerOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_2dd75be4-fcbe-4736-a4d2-bca197694277" xlink:to="loc_osur_CustomerOneMember_475da378-4821-450f-9457-474c5d032c8b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_c2bbb2cc-46e1-4613-a62c-262a49634e7f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_osur_RevenueFromContractWithCustomerTable_6fcb35df-ed8d-49bf-aad2-7a0aa3f5fac3" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_c2bbb2cc-46e1-4613-a62c-262a49634e7f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_c2bbb2cc-46e1-4613-a62c-262a49634e7f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_c2bbb2cc-46e1-4613-a62c-262a49634e7f" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_c2bbb2cc-46e1-4613-a62c-262a49634e7f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1a6443cc-32a6-4ec8-8902-121068534089" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_c2bbb2cc-46e1-4613-a62c-262a49634e7f" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1a6443cc-32a6-4ec8-8902-121068534089" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableMember_47990587-6ce7-495c-8cc1-b69122a0b708" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1a6443cc-32a6-4ec8-8902-121068534089" xlink:to="loc_us-gaap_AccountsReceivableMember_47990587-6ce7-495c-8cc1-b69122a0b708" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_5972d6b1-196b-4e23-a187-f3d6b67aefec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1a6443cc-32a6-4ec8-8902-121068534089" xlink:to="loc_us-gaap_SalesRevenueNetMember_5972d6b1-196b-4e23-a187-f3d6b67aefec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_6afd8f5c-62bd-46f7-a947-18ddf59ff26f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_osur_RevenueFromContractWithCustomerTable_6fcb35df-ed8d-49bf-aad2-7a0aa3f5fac3" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_6afd8f5c-62bd-46f7-a947-18ddf59ff26f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_6afd8f5c-62bd-46f7-a947-18ddf59ff26f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_6afd8f5c-62bd-46f7-a947-18ddf59ff26f" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_6afd8f5c-62bd-46f7-a947-18ddf59ff26f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_336653a8-c728-49c9-9f2b-383bedab6478" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_6afd8f5c-62bd-46f7-a947-18ddf59ff26f" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_336653a8-c728-49c9-9f2b-383bedab6478" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_9e3db133-7d05-4a6f-9261-6d7906d17061" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_336653a8-c728-49c9-9f2b-383bedab6478" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_9e3db133-7d05-4a6f-9261-6d7906d17061" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_5adbc926-4f98-4006-aef1-0a029ad533e1" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_osur_RevenueFromContractWithCustomerTable_6fcb35df-ed8d-49bf-aad2-7a0aa3f5fac3" xlink:to="loc_srt_RangeAxis_5adbc926-4f98-4006-aef1-0a029ad533e1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5adbc926-4f98-4006-aef1-0a029ad533e1_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_5adbc926-4f98-4006-aef1-0a029ad533e1" xlink:to="loc_srt_RangeMember_5adbc926-4f98-4006-aef1-0a029ad533e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_31e458f4-1ae5-48eb-8605-a34dbbf48f66" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_5adbc926-4f98-4006-aef1-0a029ad533e1" xlink:to="loc_srt_RangeMember_31e458f4-1ae5-48eb-8605-a34dbbf48f66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_87b06c67-0d5a-4888-b5ab-a4d0fa0b6938" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_31e458f4-1ae5-48eb-8605-a34dbbf48f66" xlink:to="loc_srt_MaximumMember_87b06c67-0d5a-4888-b5ab-a4d0fa0b6938" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerDurationAxis_12cafd1b-539a-4c2a-835b-841c4562db0f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerDurationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_osur_RevenueFromContractWithCustomerTable_6fcb35df-ed8d-49bf-aad2-7a0aa3f5fac3" xlink:to="loc_us-gaap_ContractWithCustomerDurationAxis_12cafd1b-539a-4c2a-835b-841c4562db0f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerDurationDomain_12cafd1b-539a-4c2a-835b-841c4562db0f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerDurationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerDurationAxis_12cafd1b-539a-4c2a-835b-841c4562db0f" xlink:to="loc_us-gaap_ContractWithCustomerDurationDomain_12cafd1b-539a-4c2a-835b-841c4562db0f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerDurationDomain_5b2a85ea-1f99-4d2b-b5fa-850301124ec7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerDurationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerDurationAxis_12cafd1b-539a-4c2a-835b-841c4562db0f" xlink:to="loc_us-gaap_ContractWithCustomerDurationDomain_5b2a85ea-1f99-4d2b-b5fa-850301124ec7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermContractWithCustomerMember_a011dc67-f100-4976-a7df-3007540154ce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermContractWithCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerDurationDomain_5b2a85ea-1f99-4d2b-b5fa-850301124ec7" xlink:to="loc_us-gaap_LongTermContractWithCustomerMember_a011dc67-f100-4976-a7df-3007540154ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ContractWithCustomerPaymentTypeAxis_da253417-cf3a-48c9-be08-c0936a3cb06f" xlink:href="osur-20230630.xsd#osur_ContractWithCustomerPaymentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_osur_RevenueFromContractWithCustomerTable_6fcb35df-ed8d-49bf-aad2-7a0aa3f5fac3" xlink:to="loc_osur_ContractWithCustomerPaymentTypeAxis_da253417-cf3a-48c9-be08-c0936a3cb06f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ContractWithCustomerPaymentTypeDomain_da253417-cf3a-48c9-be08-c0936a3cb06f_default" xlink:href="osur-20230630.xsd#osur_ContractWithCustomerPaymentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_osur_ContractWithCustomerPaymentTypeAxis_da253417-cf3a-48c9-be08-c0936a3cb06f" xlink:to="loc_osur_ContractWithCustomerPaymentTypeDomain_da253417-cf3a-48c9-be08-c0936a3cb06f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_ContractWithCustomerPaymentTypeDomain_08ac7fa9-837d-413c-a4d0-6099b85461f9" xlink:href="osur-20230630.xsd#osur_ContractWithCustomerPaymentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_osur_ContractWithCustomerPaymentTypeAxis_da253417-cf3a-48c9-be08-c0936a3cb06f" xlink:to="loc_osur_ContractWithCustomerPaymentTypeDomain_08ac7fa9-837d-413c-a4d0-6099b85461f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_UpFrontPaymentMember_c9921d1b-d78e-4edd-8dbb-54e043e2c36e" xlink:href="osur-20230630.xsd#osur_UpFrontPaymentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_osur_ContractWithCustomerPaymentTypeDomain_08ac7fa9-837d-413c-a4d0-6099b85461f9" xlink:to="loc_osur_UpFrontPaymentMember_c9921d1b-d78e-4edd-8dbb-54e043e2c36e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/IncomeLossPerShareAdditionalInformationDetail" xlink:type="simple" xlink:href="osur-20230630.xsd#IncomeLossPerShareAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/IncomeLossPerShareAdditionalInformationDetail" xlink:type="extended" id="i6440ff4f3fe5470b8d58491c7d1ef748_IncomeLossPerShareAdditionalInformationDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_9ebda303-06e1-4e84-a9f9-4383a63d1a10" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_0e8d041a-a2b3-4cd0-b0f6-e463e5114cf7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_9ebda303-06e1-4e84-a9f9-4383a63d1a10" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_0e8d041a-a2b3-4cd0-b0f6-e463e5114cf7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_b299e533-0a46-4eff-ac90-618012537433" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_9ebda303-06e1-4e84-a9f9-4383a63d1a10" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_b299e533-0a46-4eff-ac90-618012537433" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_63ca54a1-578f-4753-bf94-0b68ff919134" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_b299e533-0a46-4eff-ac90-618012537433" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_63ca54a1-578f-4753-bf94-0b68ff919134" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_63ca54a1-578f-4753-bf94-0b68ff919134_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_63ca54a1-578f-4753-bf94-0b68ff919134" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_63ca54a1-578f-4753-bf94-0b68ff919134_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c9fdd804-8560-45c2-a404-891859d728b4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_63ca54a1-578f-4753-bf94-0b68ff919134" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c9fdd804-8560-45c2-a404-891859d728b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_CommonStockOptionsUnvestedRestrictedStockAndUnvestedPerformanceUnitsMember_b737e9d4-4f11-42e8-9323-f25191179ad8" xlink:href="osur-20230630.xsd#osur_CommonStockOptionsUnvestedRestrictedStockAndUnvestedPerformanceUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c9fdd804-8560-45c2-a404-891859d728b4" xlink:to="loc_osur_CommonStockOptionsUnvestedRestrictedStockAndUnvestedPerformanceUnitsMember_b737e9d4-4f11-42e8-9323-f25191179ad8" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.orasure.com/role/StockholdersEquitySummaryofReconciliationofChangesinStockholdersEquityDetail" xlink:type="simple" xlink:href="osur-20230630.xsd#StockholdersEquitySummaryofReconciliationofChangesinStockholdersEquityDetail"/>
  <link:definitionLink xlink:role="http://www.orasure.com/role/StockholdersEquitySummaryofReconciliationofChangesinStockholdersEquityDetail" xlink:type="extended" id="i5179804b4310430387c50089ad1432fb_StockholdersEquitySummaryofReconciliationofChangesinStockholdersEquityDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesIssued_2e3e4236-e1f3-4741-987f-a05e0b72f4cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_SharesIssued_2e3e4236-e1f3-4741-987f-a05e0b72f4cd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_5c7928a2-1010-4ca3-b519-166e4ac2c593" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_StockholdersEquity_5c7928a2-1010-4ca3-b519-166e4ac2c593" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_634990f0-4750-4c6b-9130-cd0bbef6e877" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_634990f0-4750-4c6b-9130-cd0bbef6e877" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_7c193ab5-c62f-44f0-8214-f2f29ae8c8e5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_7c193ab5-c62f-44f0-8214-f2f29ae8c8e5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_StockIssuedDuringPeriodSharesVestingOfRestrictedStockAndPerformanceStockUnits_f3e98cff-2174-45ba-9ed0-70cab33b38dd" xlink:href="osur-20230630.xsd#osur_StockIssuedDuringPeriodSharesVestingOfRestrictedStockAndPerformanceStockUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_osur_StockIssuedDuringPeriodSharesVestingOfRestrictedStockAndPerformanceStockUnits_f3e98cff-2174-45ba-9ed0-70cab33b38dd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_StockIssuedDuringPeriodValueVestingOfRestrictedStockAndPerformanceStockUnits_0be60ef2-3e51-4f7b-bf73-45d1f28250c6" xlink:href="osur-20230630.xsd#osur_StockIssuedDuringPeriodValueVestingOfRestrictedStockAndPerformanceStockUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_osur_StockIssuedDuringPeriodValueVestingOfRestrictedStockAndPerformanceStockUnits_0be60ef2-3e51-4f7b-bf73-45d1f28250c6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_3523cda5-252c-4b76-936e-284b823a286b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_3523cda5-252c-4b76-936e-284b823a286b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_af95d589-46c7-4694-b367-f7c6294a1549" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_af95d589-46c7-4694-b367-f7c6294a1549" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_1c860e9b-9ff4-453a-b12b-36c4697511c4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_1c860e9b-9ff4-453a-b12b-36c4697511c4" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_ac8e5e7b-25ec-44c7-a76b-8ecdc7fe1e98" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_NetIncomeLoss_ac8e5e7b-25ec-44c7-a76b-8ecdc7fe1e98" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_302f275e-a908-4a70-aa74-73c5a15ce8f2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_302f275e-a908-4a70-aa74-73c5a15ce8f2" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_c0b73273-f493-4f11-9dc7-821242f966cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_c0b73273-f493-4f11-9dc7-821242f966cc" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesIssued_3761eb4d-0a27-407a-9374-17d07121bc36" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesIssued"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_83634921-2591-405d-8aab-4ce175cdc28c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_57b99963-233b-48e9-b44e-ed3f68870d08" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_906dc3d8-5610-4925-911f-c4b2691cc63f" xlink:to="loc_us-gaap_StatementTable_57b99963-233b-48e9-b44e-ed3f68870d08" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_62e07d2c-4daa-4b02-883d-d606cb4709dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_57b99963-233b-48e9-b44e-ed3f68870d08" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_62e07d2c-4daa-4b02-883d-d606cb4709dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_62e07d2c-4daa-4b02-883d-d606cb4709dc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_62e07d2c-4daa-4b02-883d-d606cb4709dc" xlink:to="loc_us-gaap_EquityComponentDomain_62e07d2c-4daa-4b02-883d-d606cb4709dc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_1dd94302-0bb8-469e-8ab7-b6d711cd3d52" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_62e07d2c-4daa-4b02-883d-d606cb4709dc" xlink:to="loc_us-gaap_EquityComponentDomain_1dd94302-0bb8-469e-8ab7-b6d711cd3d52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_03f93d29-74a8-4844-aaf4-4d31628534aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1dd94302-0bb8-469e-8ab7-b6d711cd3d52" xlink:to="loc_us-gaap_CommonStockMember_03f93d29-74a8-4844-aaf4-4d31628534aa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_6c40acc7-8199-4900-8d84-412c7edc6e06" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1dd94302-0bb8-469e-8ab7-b6d711cd3d52" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_6c40acc7-8199-4900-8d84-412c7edc6e06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_56e743fe-5490-4df3-a16f-524ec982e42e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1dd94302-0bb8-469e-8ab7-b6d711cd3d52" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_56e743fe-5490-4df3-a16f-524ec982e42e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_dd9639fe-b70d-49ed-9378-0cee3a64a8b4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1dd94302-0bb8-469e-8ab7-b6d711cd3d52" xlink:to="loc_us-gaap_RetainedEarningsMember_dd9639fe-b70d-49ed-9378-0cee3a64a8b4" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_osur_KathleenWeberMember_b755b589-2260-4c83-9faa-c083457259e9" xlink:href="osur-20230630.xsd#osur_KathleenWeberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_osur_KathleenWeberMember_b755b589-2260-4c83-9faa-c083457259e9" xlink:type="arc" order="2"/>
  </link:definitionLink>
</link:linkbase>
