The Berthelot River is a tributary of the Mégiscane River, flowing into the townships of Leigne, Valmy and Berthelot, in the territory of Senneterre, in La Vallée-de-l'Or Regional County Municipality, in the Abitibi-Témiscamingue administrative region, in Quebec, in Canada.

The Berthelot River flows entirely in forest zone, west of the Gouin Reservoir.

The west side of the Berthelot River head zone is served by a forest road from Forsythe.

This head of water is located at: The mouth of Lake Leigne is located in Leigne Township, either at 11.5 kilometres (7.1 mi) north-west of the Canadian National Railway, or at the west side of Gagnon-Siding at 70.6 kilometres (43.9 mi) east of downtown Senneterre, 133.9 kilometres (83.2 mi) west of the village center of Parent and 20.1 kilometres (12.5 mi) south-west of the confluence of the Berthelot River with the Mégiscane River.

The toponym "Berthelot River" was formalized on December 5, 1968, at the Commission de toponymie du Québec, when it was created.