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        <issuerName>Planet Fitness, Inc.</issuerName>
        <issuerTradingSymbol>PLNT</issuerTradingSymbol>
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            <rptOwnerName>Rondeau Christopher</rptOwnerName>
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            <rptOwnerStreet1>C/O PLANET FITNESS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>4 LIBERTY LANE WEST</rptOwnerStreet2>
            <rptOwnerCity>HAMPTON</rptOwnerCity>
            <rptOwnerState>NH</rptOwnerState>
            <rptOwnerZipCode>03842</rptOwnerZipCode>
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            <officerTitle>Chief Executive Officer</officerTitle>
            <otherText></otherText>
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    <footnotes>
        <footnote id="F1">On March 13, 2019, The Christopher J. Rondeau Revocable Trust of 2006, u/d/t 05/15/06 exchanged 244,167 Common Units of Pla-Fit Holdings, LLC (&quot;Holding Units&quot;) and 244,167 shares of Class B common stock of Planet Fitness, Inc. (the &quot;Company&quot;) for 244,167 shares of Class A common stock of the Company, and substantially simultaneously sold all 244,167 shares of Class A common stock of the Company in a single private sale. Following the sale, The Christopher J. Rondeau Revocable Trust of 2006, u/d/t 05/15/06 held 3,002,980 Holding Units and 3,002,980 shares of Class B common stock of the Company.</footnote>
        <footnote id="F2">On March 13, 2019, The Christopher J. Rondeau Irrevocable GST Trust of 2012, u/d/t 11/08/12 exchanged 104,643 Holding Units and 104,643 shares of Class B common stock of the Company for 104,643 shares of Class A common stock of the Company, and substantially simultaneously sold all 104,643 shares of Class A common stock of the Company in a single private sale. Following the sale, The Christopher J. Rondeau Irrevocable GST Trust of 2012, u/d/t 11/08/12 held 996,520 Holding Units and 996,520 shares of Class B common stock of the Company. Mr. Rondeau disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F3">Pursuant to the terms of the Exchange Agreement dated as of August 5, 2015, as amended, by and among the Company, Pla-Fit Holdings, LLC and the holders from time to time of Holding Units and shares of Class B common stock, the holders thereof may exchange all or a portion of their Holding Units along with an equal number of shares of Class B common stock for shares of Class A common stock of the Company on a one-to-one basis (one Holding Unit and one share of Class B common stock together exchangeable for one share of Class A common stock). The holders thereof are not required to pay an exercise price in connection with any such exchange. The Holding Units do not expire. The Class B common stock provides the holder with one vote on all matters submitted to a vote of the Company's stockholders but does not entitle the holder to any of the economic rights associated with shares of the Company's Class A common stock.</footnote>
    </footnotes>

    <remarks>Justin Vartanian is signing on behalf of Mr. Rondeau pursuant to a Power of Attorney dated July 29, 2015, which was previously filed with the Securities and Exchange Commission.</remarks>

    <ownerSignature>
        <signatureName>/s/ Justin Vartanian, Attorney-in-Fact</signatureName>
        <signatureDate>2019-03-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
