Sir Louis-Napoléon Casault (July 10, 1823 – May 18, 1908) was a Quebec lawyer, judge, professor and political figure.

He studied at the Petit Séminaire de Québec, then apprenticed in law and was admitted to the bar in 1847.

A small lake in the unorganized territory of Lac-Casault, Quebec, Canada, was named after him.

Their family residence was "Londesir" 9 de Salaberry Street, Quebec.

Lady Casault was elected the first President of the Quebec branch of the National Council of Women of Canada, when that institution was founded by Ishbel Hamilton-Gordon, Marchioness of Aberdeen and Temair.