The rivière du Grand Portage (English: Grand Portage River) is a tributary of Chigoubiche River, flowing into the unorganized territory of Lac-Ashuapmushuan in the Le Domaine-du-Roy Regional County Municipality, in the administrative region of Saguenay–Lac-Saint-Jean, in province of Quebec, in Canada.

[2] The Grand Portage River draws its source from an unidentified lake (length: 1.3 km (0.81 mi); altitude: 623 m (2,044 ft)).

This spring is located in a mountainous area in the unorganized territory of Lac-Ashuapmushuan, at: From its source, the Grand Portage river flows over 62.4 km (38.8 mi) with a drop of 273 m (896 ft), entirely in the forest zone, according to the following segments: Upper course of the Grand Portage river (37.6 km (23.4 mi) segment) Lower course of the Grand Portage river (24.8 km (15.4 mi) segment) The Grand Portage river empties on the southwest bank of the Chigoubiche River, opposite the railway.

This confluence is located at: From the mouth of the Grand Portage river, the current descends the course of the Chigoubiche river on 46.2 km (28.7 mi), the course of the Ashuapmushuan river on 59.8 km (37.2 mi), then cross lac Saint-Jean east on 41.1 km (25.5 mi) (i.e. its full length), take the course of the Saguenay River via la Petite Décharge on 172.3 km (107.1 mi) east to Tadoussac where it meets the estuary of Saint Lawrence.

[2] The toponym "rivière du Grand Portage" was made official on December 5, 1968, at the Place Names Bank of the Commission de toponymie du Québec.