The Chambly Basin is a shallow, oblong body of water formed by an enlargement of the Richelieu River, extending out from the foot of the rapids on the river between Chambly and Richelieu, in the Quebec region of Montérégie. The towns of Chambly, Richelieu, Saint-Mathias-sur-Richelieu and Carignan surround the basin.

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.