Following its Chichester run, it will also tour the UK from Oct. 1 to Dec. 6.
LaChance's other stage credits include Johnny Baseball, Central Avenue Breakdown and If You Give a Mouse a Cookie.
In a press statement, Jonathan Church, Chichester's artistic director who is also directing the show, commented, "Mabel Normand was ‘discovered’ by Mack Sennett and became one of the best loved female film stars of the era. Partly for this reason Michael [Ball] and I always hoped we might cast an emerging young actress to play Mabel. And we are thrilled that Rebecca will follow in the steps of Bernadette Peters and Imelda Staunton who played this role at the beginning of their careers."
Further casting also includes Anna-Jane Casey as Lottie, Jack Edwards as Fatty, Alex Giannini as Mr Kleiman, Gunnar Cauthery as Frank and Mark Inscoe as William Desmond Taylor. The company also includes Michelle Francis, Emily Langham, Rebecca Louis, Joshua Lovell, Joseph Prouse, and Emily Shaw.
Further casting is to be announced.