The French River is a river in Central Ontario, Canada. It flows 110 kilometres from Lake Nipissing southwest to Georgian Bay. The river largely follows the boundary between the Parry Sound District and the Sudbury District, and in most contexts is considered the dividing line between Northern and Southern Ontario. The French River was desiā¦The French River is a river in Central Ontario, Canada. It flows 110 kilometres from Lake Nipissing southwest to Georgian Bay. The river largely follows the boundary between the Parry Sound District and the Sudbury District, and in most contexts is considered the dividing line between Northern and Southern Ontario. The French River was designated a Canadian Heritage River in 1986.