King's Highway 16, commonly referred to as Highway 16 and historically as the Prescott Highway, is a provincially maintained highway in the Canadian province of Ontario. The highway once travelled from near Prescott to Ottawa, traversing the distance between the St. Lawrence River and the Ottawa River. However, its length was truncated significantly when most of the route was twinned with a second roadway, and renumbered as Highway 416. A short stub remains through Johnstown, crossing the St. Lawrence on the Ogdensburg–Prescott International Bridge to Ogdensburg, New York, where it becomes New York State Route 812.