King's Highway 409, commonly referred to as Highway 409 and historically as the Belfield Expressway, is a 400-series highway in the Canadian province of Ontario that extends from Highway 401 in Toronto to Pearson International Airport, west of Highway 427, in Mississauga. It is a short freeway used mainly as a spur route bypass for traffic approaching the airport or Highway 427 northbound from Highway 401 westbound, as both are not accessible at the complex interchange between Highways 401 and 427.