Saint Lawrence, Gulf of

Inlet of the Atlantic Ocean at the mouth of the St Lawrence River. Measuring roughly 765 km/475 mi by 445 km/275 mi, it is bounded on the north by the North Shore (Côte-Nord) of Québec, on the west by the Gaspé Peninsula and New Brunswick, on the south by Nova Scotia, and on the east by Newfoundland. Together with the St Lawrence River, it forms the historic gateway into Canada through which the first explorers came to settle and develop the country.

The two main islands in the Gulf of St Lawrence are L'Île d'Anticosti (Anticosti Island) in the north, which belongs to Québec and stands at the mouth of the St Lawrence River, and the province of Prince Edward Island in the southwest. Northeast of Prince Edward Island lie the Magdalen Islands (Îles de la Madeleine), which are part of Québec. Chaleur Bay (Baie des Chaleurs) is a western arm of the gulf, south of the Gaspé. The gulf connects with the ocean via the Strait of Belle Isle in the northeast, between Labrador and Newfoundland, and via Cabot Strait in the southeast, between Newfoundland and Cape Breton Island, Nova Scotia. It receives a huge volume of fresh water from the river that gives it its name. With extensive deeps and shallows, and crossed (northwest–southeast) by the Laurentian Channel, it is an important fishing ground. For a long time, it was inhabited by the Inuit (on its northern shores), the Micmac (in the south), and the Beothuk (in the east). Basque whalers and fishermen began to arrive in the gulf from about 1525 onwards, and it was explored by Jacques Cartier in 1534.