Rivière Saint-François, 280 km long, drainage basin 10 230 km2, is located in southern Québec. Named in 1635 in honour of François de Lauson, eldest son of the fourth governor of New France, it was called Alsigântekw, "river of the drifting plants" or "shelly river," by the Abenaki.

The river originates in Lac Saint-François, 48 km northwest of Lac Mégantic, in the forested or agro-forested Appalachian region. It flows in a southwest direction through Lac Aylmer towards Lennoxville and Sherbrooke, where it is joined by Rivière Magog. Now flowing to the northwest, it reaches the St. Lawrence Lowland in the agricultural region north of Drummondville before flowing into Lac Saint-Pierre. As early as 1670, the river was used by the Abenaki and the French. However, the major part of the Saint-François basin was not opened up to colonization until the end of the 18th century.