The Grand-Saint-Louis river flows in the territory of the town of Bécancour, in the Bécancour Regional County Municipality, in the administrative region of Centre-du-Québec, in the province of Quebec, in Canada.

The main hydrographic slopes neighboring the "Grand-Saint-Louis river" are: The "Grand-Saint-Louis river" originates in an agricultural area on the border of Saint-Sylvère and Bécancour.

This area is located near the Route des Peupliers, north of the Bécancour River and west of the village of Bécancour.

From the intermunicipal limit between Saint-Sylvère and Bécancour, the course of the river flows in forest and agricultural area, over 12.9 km, with a drop of 60 metres (200 ft), according to the following segments: The Grand-Saint-Louis river flows on the west bank of the Gentilly South-West River.

The term "Saint-Louis" constitutes a family name of French origin.