A-20 is Québec's longest Autoroute, stretching from the Canadian border near Cornwall, Ontario through Montréal and the Québec City area before ending near Rivière-du-Loup. There is also a disconnected section of A-20 farther east running between Rimouski and Mont-Joli. For most of its length, A-20 carries the Autoroute Jean-Lesage and Trans-Canada designations.
Western Terminus: Junction of King's Highway 401 at the Canada/Québec border near Rivière-Beaudette.
Eastern Terminus: Junction of R-132 near Rivière-du-Loup.