The Tremblay river is a tributary of the rivière aux Anglais flowing in the unorganized territory Rivière-aux-Outardes, in the Manicouagan Regional County Municipality, in the administrative region of Côte-Nord, in the province of Quebec, in Canada.

The Tremblay River rises on the Canadian Shield, at Lac Alex (length: 0.4 km (0.25 mi); altitude: 350 m (1,150 ft)).

This eastern forest lake has two outlets: that of the north (at the bottom of a bay) turns out to be the beginning of a stream leading north to the Françoise River; that of the south (at the bottom of a bay) turns out to be the head of the Tremblay river.

The southern mouth of Lac Alex is located 5.4 km (3.4 mi) north of the confluence of the Tremblay and English rivers, 5.3 km (3.3 mi) northwest of head lake of the Mistassini River and 26.1 km (16.2 mi) north-west of the confluence of the rivière aux Anglais and the Baie des Anglais on the north shore of the Gulf of St. Lawrence.

The toponym "Tremblay River" was formalized on August 2, 1974, at the Place Names Bank of the Commission de toponymie du Québec.