content: <?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
    <headerData>
      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001073385</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
      </filerInfo>
    </headerData>
    <formData>
      <issuerInfo>
        <issuerCik>0000874015</issuerCik>
        <issuerName>IONIS PHARMACEUTICALS INC</issuerName>
        <secFileNumber>000-19125</secFileNumber>
        <issuerAddress>
          <com:street1>2855 GAZELLE COURT</com:street1>
          <com:city>CARLSBAD</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>92010</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>7609319200</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>PARSHALL B LYNNE</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Director</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>COMMON STOCK</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>INSIGHT SECURITIES, INC.</name>
          <address>
            <com:street1>600 CENTRAL</com:street1>
            <com:street2>STE 293</com:street2>
            <com:city>HIGHLAND PARK</com:city>
            <com:stateOrCountry>IL</com:stateOrCountry>
            <com:zipCode>60035</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>10000</noOfUnitsSold>
        <aggregateMarketValue>451268.00</aggregateMarketValue>
        <noOfUnitsOutstanding>143100000</noOfUnitsOutstanding>
        <approxSaleDate>09/26/2023</approxSaleDate>
        <securitiesExchangeName>NYSE</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>COMMON STOCK</securitiesClassTitle>
        <acquiredDate>01/15/2020</acquiredDate>
        <natureOfAcquisitionTransaction>COMPENSATION</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>IONIS PHARMACEUTICALS, INC.</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>10000</amountOfSecuritiesAcquired>
        <paymentDate>01/15/2020</paymentDate>
        <natureOfPayment>COMPENSATION</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <remarks>INSIGHT SECURITIES SOLD 10,000 SHARES OF IONIS PHARMACEUTICALS, INC FOR LYNNE PARSHALL</remarks>
      <noticeSignature>
        <noticeDate>09/26/2023</noticeDate>
        <planAdoptionDates>
          <planAdoptionDate>11/14/2022</planAdoptionDate>
        </planAdoptionDates>
        <signature>MICHAEL MAKULA</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
metadata_documents: [{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 2998}]
text: 144
  0001073385
  XXXXXXXX
  LIVE
  0000874015
  IONIS PHARMACEUTICALS INC
  000-19125
  2855 GAZELLE COURT
  CARLSBAD
  CA
  92010
  7609319200
  PARSHALL B LYNNE
  Director
  COMMON STOCK
  INSIGHT SECURITIES, INC.
  600 CENTRAL
  STE 293
  HIGHLAND PARK
  IL
  60035
  10000
  451268.00
  143100000
  09/26/2023
  NYSE
  COMMON STOCK
  01/15/2020
  COMPENSATION
  IONIS PHARMACEUTICALS, INC.
  N
  10000
  01/15/2020
  COMPENSATION
  Y
  INSIGHT SECURITIES SOLD 10,000 SHARES OF IONIS PHARMACEUTICALS, INC FOR LYNNE PARSHALL
  09/26/2023
  11/14/2022
  MICHAEL MAKULA