series of eight butte-type mountains in the St. Lawrence River valley, in Montréal, Montérégie, and Estrie regions, southeastern Quebec province, Canada. The hills extend eastward for about 50 miles (80 km) from Île de Montréal to the Appalachian Highlands. Formed of igneous rock, the hills are characterized by high crests on their northeast sides and gradual slopes on the southwest. The name, derived from the Latin Mons Regius (“Royal Mountain”), was first applied by Jacques Cartier, the French explorer, in 1535.

Best known is Mont-Royal, on Île de Montréal, which actually consists of three peaks—Mont-Royal (763 feet 【233 m】), Westmount, and Côte-des-Neiges. Extending into Montérégie and Estrie are the mountains of Saint-Bruno, Saint-Hilaire (Beloeil), Saint-Grégoire (Johnson), Brome, Rougemont, Yamaska, and Shefford.