Montreal has an excellent harbor on the St. Lawrence Seaway, which connects the city to the great industrial centers of the Great Lakes. As Canada's most important port, it is a transshipment point for oil, grain, sugar, machinery, and manufactured goods. It is also an important railway hub, and has two international airports, Dorval and Mirabel. Its underground rail system, the Métro, was inaugurated in 1966. The city's industries include pharmaceuticals, high-technology, steel, electronic equipment, refined petroleum, transportation equipment, textiles, clothing, food and beverages, printed materials, and tobacco. It is also a financial service center, which greatly expanded in the 1980s.

Once Canada's preeminent city, Montreal has been eclipsed by Toronto as the country's economic center. Tensions over Quebec's insistence on enforcing its francophone culture have caused an outmigration of English-speaking people to Ontario and to the growing western provinces. Despite these changes, Montreal remains one of North America's great cosmopolitan cities.

The city lies at the foot of Mt. Royal, which is the source of its name and around which extends a large wooded park in the center of the city. To the south fronting the river is the area of Old Montreal, which draws visitors to the boardwalk on the site of the Old Port and to Place Jacques-Cartier, St. Sulpice Seminary (1685), the Château de Ramezay (1705), and the Gothic Church of Notre Dame (c.1820). Beginning in the 1960s, following a period of neglect, Old Montreal underwent extensive renovation and gained commercial, government, and private tenants. Located in the downtown area is the Place Ville Marie, an innovative commercial complex built in 1962; around it stretches the Underground City, which provides protected access, both above and below street level, to shopping, restaurants, offices, and other commercial enterprises and to transportation links. Montreal has a museum of fine arts, a museum of contemporary arts, an environmental museum and insectarium, and large botanical gardens. An amusement center and casino occupy the site of Expo '67. The city is the seat of McGill Univ., the Univ. of Montreal, the Univ. of Quebec at Montreal, and Concordia Univ. The National Hockey League's hallowed Canadiens and the Canadian Football League's Alouettes play in the city.

A stockaded Native American village, Hochelaga, was found on the site (1535) by Cartier, and the island was visited in 1603 by Champlain, but it was not settled by the French until 1642, when a band of priests, nuns, and settlers under Paul de Chomedey, sieur de Maisonneuve, founded the Ville Marie de Montréal. The settlement grew to become an important center of the fur trade and the starting point for the western expeditions of Jolliet, Marquette, La Salle, Vérendrye, and Duluth. It was fortified in 1725 and remained in French possession until 1760, when Vaudreuil de Cavagnal surrendered it to British forces under Amherst. Americans under Richard Montgomery occupied it briefly (1775–76) during the American Revolution.

The city's growth was aided by the opening in 1825 of the Lachine Canal, making possible water communications with the Great Lakes. From 1844 to 1849, Montreal was the capital of United Canada. The Canadian Pacific Railway established its headquarters here in the 1880s. Montreal held the much-praised international exposition of 1967, known as Expo '67, and further increased its international stature by hosting the 1976 Summer Olympics, although the provincial debt incurred in undertaking the latter was not retired until 2006.