Saint-Jean-sur-Richelieu is a city in eastern Montérégie in the Canadian province of Quebec, about 40 kilometres (25 mi) southeast of Montreal, located roughly halfway between Montreal and the Canada–United States border with the state of Vermont. It is situated on both the west and east banks of the Richelieu River at the northernmost navigable point of Lake Champlain. As of December 2019, the population of Saint-Jean-sur-Richelieu was 98,036.

The Richelieu River is a river of Quebec, Canada, and a major right-bank tributary of the St. Lawrence River. It rises at Lake Champlain, from which it flows northward through Quebec and empties into the St. Lawrence. It was formerly known by the French as the Iroquois River and the Chambly River, and was named for Cardinal Richelieu, the powerful minister under Louis XIII.