Route 138 is a major highway in the Canadian province of Quebec, following the entire north shore of the Saint Lawrence River past Montreal to the eastern terminus in Kegashka on the Gulf of Saint Lawrence. The western terminus is in Elgin, at the border with New York State south-west of Montreal (connecting with New York State Route 30 at the Trout River Border Crossing). Part of this highway is known as the Chemin du Roy, or King's Highway, which is one of the oldest highways in Canada. A third segment of Route 138 extends from Old Fort to Blanc-Sablon on the eastern end of the Côte-Nord.