<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2015-08-06</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001637207</issuerCik>
        <issuerName>Planet Fitness, Inc.</issuerName>
        <issuerTradingSymbol>PLNT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001361944</rptOwnerCik>
            <rptOwnerName>Spinelli Stephen JR</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O PLANET FITNESS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>26 FOX RUN ROAD</rptOwnerStreet2>
            <rptOwnerCity>NEWINGTON</rptOwnerCity>
            <rptOwnerState>NH</rptOwnerState>
            <rptOwnerZipCode>03801</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Holding Units and Class B common stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F3"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A common stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>149052</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The Common Units of Pla-Fit Holdings, LLC  (&quot;Holding Units&quot;) and shares of Class B common stock of Planet Fitness, Inc. (the &quot;Company&quot;) reported herein were issued pursuant to a reclassification of Pla-Fit Holdings, LLC on August 5, 2015. Mr. Spinelli holds an aggregate of 149,052 Holding Units and 149,052 shares of Class B common stock of the Company.</footnote>
        <footnote id="F2">Represents an equity award granted to Mr. Spinelli on April 30, 2013 under the Pla-Fit Holdings, LLC 2013 Equity Incentive Plan that was converted into Holding Units in connection with the reclassification of Pla-Fit Holdings, LLC described above. Eighty percent of the award vests annually in equal installments over five years from a specified vesting date, and twenty percent vests in connection with the Company's initial public offering, subject generally to remaining in service on the applicable vesting date.</footnote>
        <footnote id="F3">Pursuant to the terms of the Exchange Agreement dated as of August 5, 2015 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, Mr. Spinelli may exchange all or a portion of his vested Holding Units along with an equal number of his shares of Class B common stock for shares of Class A common stock of the Company on a one-to-one basis (one vested Holding Unit and one share of Class B common stock together exchangeable for one share of Class A common stock). The Holding Units will expire on April 30, 2023 and the holders thereof are not required to pay an exercise price in connection with any such exchange. 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 Stephen Spinelli pursuant to a Power of Attorney dated July 29, 2015, which is attached hereto as an exhibit.</remarks>

    <ownerSignature>
        <signatureName>/s/ Justin Vartanian, attorney-in-fact</signatureName>
        <signatureDate>2015-08-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
