King's Highway 103, commonly referred to as Highway 103, was a provincially maintained highway in the Canadian province of Ontario. Located in the District Municipality of Muskoka and Simcoe County, the highway extended from Highway 12 at Waubaushene to Highway 69 at Foot's Bay. Established in 1944, it was originally a short gravel highway connecting Waubaushene to Port Severn. In 1950 it was chosen as the future route of the Trans-Canada Highway and extended to Foot's Bay. It existed until 1976, when a series of renumberings eliminated the designation, replacing it with Highway 69; Highway 400 has since been built over the majority of the former route.