The rivière Trois Milles (French pronunciation: [ʁivjɛʁ tʁwa mil], "Three Mile River") is a tributary of Lake Saint-Georges (which is crossed by the Gamache River), flowing in the municipality of L'Île-d'Anticosti, in the Minganie Regional County Municipality, in the administrative region of Côte-Nord, in province of Quebec, in Canada.

The main forest road on Anticosti Island that starts from Port-Menier goes up this valley and cuts the river just south of Princeton Lake.

[1] The Trois Milles River has its source at Princeton Lake (length: 1.4 km (0.87 mi); altitude: 81 m (266 ft)) located in the western part of Anticosti Island.

From the mouth of Princeton Lake, the course of the Trois Milles River descends on 13.9 km (8.6 mi), with a drop of 80 m (260 ft), according to the following segments: This confluence is located at 14.4 km (8.9 mi) east of the Pointe aux Pointe-Ouest point of Anticosti Island, at 11.3 km (7.0 mi) southeast of the shore north of the island and 1.4 km (0.87 mi) north of Gamache Bay.

[1] This toponymic designation is based on the fact that the road leading to the airport crosses this watercourse three miles from the center of the village of Port-Menier.