content: <?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
    <!-- Generated by Workiva -->
    <headerData>
      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001609405</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
      </filerInfo>
    </headerData>
    <formData>
      <issuerInfo>
        <issuerCik>0001805890</issuerCik>
        <issuerName>Fusion Pharmaceuticals, Inc.</issuerName>
        <secFileNumber>001-39344</secFileNumber>
        <issuerAddress>
          <com:street1>270 Longwood Rd., S.</com:street1>
          <com:city>Hamilton, Ontario</com:city>
          <com:stateOrCountry>Z4</com:stateOrCountry>
          <com:zipCode>L8P 0A6</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>289-799-0891</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Chau Q. Khuong</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Affiliate</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>J.P. Morgan Securities LLC</name>
          <address>
            <com:street1>390 Madison Avenue - 6th Floor</com:street1>
            <com:city>New York</com:city>
            <com:stateOrCountry>NY</com:stateOrCountry>
            <com:zipCode>10017</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>22093</noOfUnitsSold>
        <aggregateMarketValue>121511</aggregateMarketValue>
        <noOfUnitsOutstanding>72405840</noOfUnitsOutstanding>
        <approxSaleDate>12/14/2023</approxSaleDate>
        <securitiesExchangeName>NASDAQ</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <acquiredDate>11/11/2022</acquiredDate>
        <natureOfAcquisitionTransaction>Open Market Purchase</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Open Market Purchase</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>22093</amountOfSecuritiesAcquired>
        <paymentDate>11/13/2022</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Chau Khuong</name>
          <address>
            <com:street1>C/o Issuer</com:street1>
            <com:street2>270 Longwood Rd., S.</com:street2>
            <com:city>Hamilton, Ontario</com:city>
            <com:stateOrCountry>Z4</com:stateOrCountry>
            <com:zipCode>L8P 0A6</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Common</securitiesClassTitle>
        <saleDate>12/08/2023</saleDate>
        <amountOfSecuritiesSold>20000</amountOfSecuritiesSold>
        <grossProceeds>115406</grossProceeds>
      </securitiesSoldInPast3Months>
      <noticeSignature>
        <noticeDate>12/14/2023</noticeDate>
        <signature>/s/ J.P. Morgan Securities LLC as agent and attorney-in-fact for Chau Q. Khuong</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
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text: 144
  0001609405
  XXXXXXXX
  LIVE
  0001805890
  Fusion Pharmaceuticals, Inc.
  001-39344
  270 Longwood Rd., S.
  Hamilton, Ontario
  Z4
  L8P 0A6
  289-799-0891
  Chau Q. Khuong
  Affiliate
  Common
  J.P. Morgan Securities LLC
  390 Madison Avenue - 6th Floor
  New York
  NY
  10017
  22093
  121511
  72405840
  12/14/2023
  NASDAQ
  Common
  11/11/2022
  Open Market Purchase
  Open Market Purchase
  N
  22093
  11/13/2022
  Cash
  N
  Chau Khuong
  C/o Issuer
  270 Longwood Rd., S.
  Hamilton, Ontario
  Z4
  L8P 0A6
  Common
  12/08/2023
  20000
  115406
  12/14/2023
  /s/ J.P. Morgan Securities LLC as agent and attorney-in-fact for Chau Q. Khuong