Quebec Route 138

Route 138 is a major highway in the Canadian province of Quebec, following the entire north shore of the St. Lawrence River past Montreal to the temporary eastern terminus in Kegashka on the Gulf of St. 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.

It passes through the Montérégie, Montreal, Lanaudière, Mauricie, Capitale-Nationale and Côte-Nord regions of Quebec. In Montreal, Highway 138 runs via Sherbrooke Street, crosses the Pierre Le Gardeur Bridge to Charlemagne and remains a four-lane road until exiting Repentigny.

This highway takes a more scenic route than the more direct Autoroute 40 between Montreal and Quebec City. It crosses the Saguenay River via a ferry which travels between Baie-Sainte-Catherine and Tadoussac; in the event of a closure of this ferry, drivers must take a significant detour via Quebec Route 172 and Quebec Route 170 to the city of Saguenay in order to cross the river by bridge.