Le Gros Bras (English: The Big Arm) is a tributary of the eastern bank of the lower part of the rivière du Gouffre, flowing in the unorganized territory of Lac-Pikauba and the municipality of Saint-Urbain, in the Charlevoix Regional County Municipality, in the administrative region of Capitale-Nationale, in the province of Quebec, in Canada.

This valley is mainly served by the route 138 whose segment near the Saint-Laurent river is designated boulevard Monseigneur de Laval; then consecutively going up north rue Saint-Édouard in Saint-Urbain, chemin Saint-François entering the forest zone, then "chemin du Parc-des-Grands-Jardins" further north.

The water level of the river varies with the seasons and the precipitation; the spring flood generally occurs in April.

This source of the river is located at: From its source, the course of Le Gros Bras descends on 22.4 kilometres (13.9 mi) in a generally deep valley, with a drop of 518 metres (1,699 ft), according to the following segments: The Gros Bras flows downstream from a river loop on the west bank of the Rivière du Gouffre, in the municipality of Saint-Urbain.

The toponym "Le Gros Bras" was formalized on December 5, 1968 at the Place Names Bank of the Commission de toponymie du Québec.