The Otter River (French: Rivière à la Loutre) is a tributary of the Northwest Branch Saint John River, flowing in Quebec (Canada) and in Maine (United States).

This river crosses the following administrative territories: The "Otter River" mostly flows Southeast into forest areas, in a small valley and crosses the Canada-US border.

This source is located at 4.3 kilometres (2.7 mi) Northeast from the village of Saint-Fabien-de-Panet, Quebec.

Finally, the current flows on the North bank of the Bay of Fundy which opens to the southwest on the Atlantic Ocean.

The place name "Otter River" was formalized December 5, 1968, at the Commission de toponymie du Québec (Quebec Places Names Board).