The MacDonald River is a tributary of the east bank of the Métabetchouane River, flowing in the municipalities of Métabetchouan–Lac-à-la-Croix and Desbiens, in the Lac-Saint-Jean-Est Regional County Municipality, in the administrative region of Saguenay–Lac-Saint-Jean, in the province, in Quebec, Canada.

Agriculture is the main economic activity in this area; recreational tourism, second.

The main watersheds adjacent to the MacDonald River are: The MacDonald River originates at the confluence of two agricultural and forestry streams, located west of Chemin du 4e rang de Métabetchouan–Lac-à-la-Croix.

From its source, the course of the MacDonald River descends on 8.0 km (5.0 mi), with a drop of 69 m (226 ft), according to the following segments: From the confluence of the MacDonald River, the current crosses 0.8 km (0.50 mi) northwest to Métabetchouane harbor, to the south shore of lac Saint-Jean; from there, the current crosses the latter on 22.8 km (14.2 mi) towards the northeast, then borrows the course of the Saguenay River via la Petite Décharge on 172.3 km (107.1 mi) until Tadoussac where it merges with the Saint Lawrence estuary.

[1] The toponym "MacDonald River" was formalized on December 5, 1968, at the Place Names Bank of the Commission de toponymie du Québec.