King's Highway 400, commonly referred to as Highway 400, historically as the Toronto–Barrie Highway, and colloquially as the 400, is a 400-series highway in the Canadian province of Ontario linking the city of Toronto in the urban and agricultural south of the province with the scenic and sparsely populated central and northern regions. The portion of the highway between Toronto and Lake Simcoe roughly traces the route of a historic trail between the Lower and Upper Great Lakes. Highway 400 is part of the highest-capacity route from southern Ontario to the Canadian West, via a connection with the Trans-Canada Highway in Sudbury. The highway also serves as the primary route from Toronto to southern Georgian Bay and Muskoka, areas collectively known as cottage country. The highway is patrolled by the Ontario Provincial Police and has a speed limit of , except for the section south of the 401, where the speed limit is .