The Atimokateiw River is a tributary of the south shore of the Gouin Reservoir, flowing into the territory of the town of La Tuque, in the area of Mauricie, Quebec, Canada.

A forest road branch serves the valley of the Atimokateiw River and the peninsula which stretches north on 30.1 kilometres (18.7 mi).

The surface of the Atimokateiw River is usually frozen from mid-November to the end of April, however, safe ice circulation is generally from early December to late March.

The Atimokateiw River originates at the mouth of an unidentified lake (length: 0.8 kilometres (0.50 mi) altitude: 469 metres (1,539 ft)).

The mouth of this head lake is located at: From the mouth of the head lake, the course of the Atimokateiw River flows over 14.6 kilometres (9.1 mi) according to the following segments: The confluence of the "Atimokateiw River" with the Gouin Reservoir is located at: The Atimokateiw River flows south of a bay stretching northward 2.9 kilometres (1.8 mi), which is an extension to the east of the Gouin Reservoir; this bay is barred on the east side by a peninsula stretching northward on 1.6 kilometres (0.99 mi).