Lachine is a borough (arrondissement) within the city of Montreal on the Island of Montreal in southwestern Quebec, Canada.

Montreal is the second most populous city in Canada, the tenth most populous city in North America, and the most populous city in the province of Quebec. Founded in 1642 as Ville-Marie, or "City of Mary", it is named after Mount Royal, the triple-peaked hill around which the early city of Ville-Marie was built. The city is centred on the Island of Montreal, which obtained its name from the same origin as the city, and a few much smaller peripheral islands, the largest of which is Île Bizard. The city is 196 km (122 mi) east of the national capital, Ottawa, and 258 km (160 mi) southwest of the provincial capital, Quebec City.