The Saint-Maurice River, or the Saint-Maurice River, is one of the main tributaries of the St. Lawrence River, after the Ottawa and the Saguenay Rivers and drains an area of 42,735 km2. It touches the Lake Saint John watershed to the north; the Nottaway River watershed, a major tributary of James Bay, to the northwest; and the southwestern tributaries of the Ottawa River. The Saint-Maurice River is located on the north shore of the St. Lawrence River in Quebec, Canada.

The St. Lawrence River is a large international river in the middle latitudes of North America connecting the Great Lakes to the North Atlantic Ocean. Its waters flow in a northeasterly direction from Lake Ontario to the Gulf of St. Lawrence, traversing Ontario and Quebec in Canada and New York in the United States. A section of the river demarcates the Canada–U.S. border.