<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:ns2="http://www.sec.gov/edgar/common">
    <headerData>
        <submissionType>144</submissionType>
        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001801372</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0001649904</issuerCik>
            <issuerName>RHYTHM PHARMACEUTICALS INC</issuerName>
            <secFileNumber>001-38223</secFileNumber>
            <issuerAddress>
                <ns2:street1>222 Berkeley Street, 12th Floor</ns2:street1>
                <ns2:city>BOSTON</ns2:city>
                <ns2:stateOrCountry>MA</ns2:stateOrCountry>
                <ns2:zipCode>02116</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>8572644280</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>JENNIFER KAYDEN LEE</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Officer</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC Executive Financial Services</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>8th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>66861</noOfUnitsSold>
            <aggregateMarketValue>4501751.13</aggregateMarketValue>
            <noOfUnitsOutstanding>61457069</noOfUnitsOutstanding>
            <approxSaleDate>11/11/2024</approxSaleDate>
            <securitiesExchangeName>NASDAQ</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>11/11/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Exercise of Stock Options</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>60981</amountOfSecuritiesAcquired>
            <paymentDate>11/11/2024</paymentDate>
            <natureOfPayment>Cash</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>02/01/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock Units</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>5880</amountOfSecuritiesAcquired>
            <paymentDate>02/01/2024</paymentDate>
            <natureOfPayment>N/A</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <remarks>The securities to be sold were acquired upon the vesting of restricted stock units during the period of  02/01/2024 through 02/22/2024

Sales that were executed on November 11, 2024 are being reported on this Form 144 filed on November 12, 2024 given the EDGAR system was not accepting filings November 11, 2024 in observance of the federal holiday.
</remarks>
        <noticeSignature>
            <noticeDate>11/11/2024</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>08/08/2024</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Jennifer Kayden Lee</signature>
        </noticeSignature>
    </formData>
</edgarSubmission>
[{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 4291}]
144
0001801372
XXXXXXXX
LIVE
0001649904
RHYTHM PHARMACEUTICALS INC
001-38223
222 Berkeley Street, 12th Floor
BOSTON
MA
02116
8572644280
JENNIFER KAYDEN LEE
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
66861
4501751.13
61457069
11/11/2024
NASDAQ
Common
11/11/2024
Exercise of Stock Options
Issuer
N
60981
11/11/2024
Cash
Common
02/01/2024
Restricted Stock Units
Issuer
N
5880
02/01/2024
N/A
Y
The securities to be sold were acquired upon the vesting of restricted stock units during the period of  02/01/2024 through 02/22/2024

Sales that were executed on November 11, 2024 are being reported on this Form 144 filed on November 12, 2024 given the EDGAR system was not accepting filings November 11, 2024 in observance of the federal holiday.
11/11/2024
08/08/2024
/s/ Jennifer Kayden Lee