French River, also known by the French equivalent Rivière des Français, is a municipality in the Canadian province of Ontario, in the Sudbury …French River, also known by the French equivalent Rivière des Français, is a municipality in the Canadian province of Ontario, in the Sudbury District. The municipality had a population of 2,828 in the 2021 Canadian census. It was formed on January 1, 1999, through the merger of the Township of Cosby, Mason and Martland and surrounding unincorporated portions of the Unorganized South Sudbury District. It was named after the French River, which flows through the municipality.