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  <headerData>
    <submissionType>13F-HR/A</submissionType>
    <filerInfo>
      <liveTestFlag>LIVE</liveTestFlag>
      <filer>
        <credentials>
          <cik>0001352851</cik>
          <ccc>XXXXXXXX</ccc>
        </credentials>
      </filer>
      <periodOfReport>09-30-2018</periodOfReport>
    </filerInfo>
  </headerData>
  <formData>
    <coverPage>
      <reportCalendarOrQuarter>09-30-2018</reportCalendarOrQuarter>
      <isAmendment>true</isAmendment>
      <amendmentNo>1</amendmentNo>
      <amendmentInfo>
        <amendmentType>RESTATEMENT</amendmentType>
        <confDeniedExpired>false</confDeniedExpired>
      </amendmentInfo>
      <filingManager>
        <name>Magnetar Financial LLC</name>
        <address>
          <ns1:street1>1603 ORRINGTON AVE.</ns1:street1>
          <ns1:street2>13TH FLOOR</ns1:street2>
          <ns1:city>EVANSTON</ns1:city>
          <ns1:stateOrCountry>IL</ns1:stateOrCountry>
          <ns1:zipCode>60201</ns1:zipCode>
        </address>
      </filingManager>
      <reportType>13F HOLDINGS REPORT</reportType>
      <form13FFileNumber>028-11800</form13FFileNumber>
      <provideInfoForInstruction5>Y</provideInfoForInstruction5>
      <additionalInformation>Confidential information was not omitted from the public Form 13F filed on November 14, 2018 for the quarter ended September 30, 2018, the box stating as such on the Form 13F Summary Page was inadvertently checked. No other amendments have been made.</additionalInformation>
    </coverPage>
    <signatureBlock>
      <name>MICHAEL TURRO</name>
      <title>Chief Compliance Officer</title>
      <phone>847-905-4690</phone>
      <signature>MICHAEL TURRO</signature>
      <city>EVANSTON</city>
      <stateOrCountry>IL</stateOrCountry>
      <signatureDate>02-14-2019</signatureDate>
    </signatureBlock>
    <summaryPage>
      <otherIncludedManagersCount>1</otherIncludedManagersCount>
      <tableEntryTotal>494</tableEntryTotal>
      <tableValueTotal>5540411</tableValueTotal>
      <isConfidentialOmitted>false</isConfidentialOmitted>
      <otherManagers2Info>
        <otherManager2>
          <sequenceNumber>1</sequenceNumber>
          <otherManager>
            <cik>0001520339</cik>
            <form13FFileNumber>028-14458</form13FFileNumber>
            <name>MTP Energy Management LLC</name>
          </otherManager>
        </otherManager2>
      </otherManagers2Info>
    </summaryPage>
  </formData>
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