The Gamache River is a watercourse flowing successively in the municipality of Saint-Valérien and the Le Bic sector of the town of Rimouski, in the Rimouski-Neigette Regional County Municipality, in the administrative region of Bas-Saint-Laurent, in Quebec, Canada.

The Gamache River is a tributary on the east bank of the rivière du Bic, which flows northeast to the southeast coast of the Saint Lawrence River and flows into the city of Rimouski.

[1] The Gamache River takes its source from agricultural and forest streams in the fifth rang East, in Saint-Valérien, in the Notre Dame Mountains.

The term "Gamache" constitutes a family name of French origin.

The toponym "rivière Gamache" was formalized on December 5, 1968, at the Commission de toponymie du Québec.