The Saguenay River is a major river of Quebec, Canada. It drains Lac Saint-Jean in the Laurentian Highlands, leaving at Alma and running east; the city of Saguenay is located on the river. It drains into the Saint Lawrence River. Tadoussac, founded as a French colonial trading post in 1600, is located on the northeast bank at this site.

The river has a very high flow-rate and is bordered by steep cliffs associated with the Saguenay Graben. Tide waters flow in its fjord upriver as far as Chicoutimi (about 100 kilometres). Many Beluga whales breed in the cold waters at its mouth, making Tadoussac a popular site for whale watching and sea kayaking; Greenland sharks also frequent the depths of the river. The area of the confluence of the Saguenay and Saint Lawrence is protected by the Saguenay–St. Lawrence Marine Park, one of Canada's national parks.