It drains Lac Saint-Jean in the Laurentian Highlands, leaving at Alma and running east; the city of Saguenay is located on the river.

Tadoussac, founded as a French colonial trading post in 1600, is located on the northeast bank at this site.

First Nations people, including Innus, have inhabited the Saguenay Fjord area for thousands of years prior to the first Europeans arriving.

Beginning in the 19th century, the river was exploited for transport and power by the logging and pulp and paper industries.

A dam on the upper Saguenay generates hydroelectricity for local industries, such as aluminum smelting and paper mills.

It begins in the form of a reservoir several kilometers long, unlike the rapids and powerful falls that dotted the river before the erection of dams.

On the northern watercourse, there is the Shipshaw hydroelectric station[14] and, on the south side, the Chute-à-Caron power plant.