The Gouin Reservoir (in French: Réservoir Gouin) is a man-made lake in the central portion of the Canadian province of Quebec, fully within the boundaries of the City of La Tuque. It is not one contiguous body of water, but the collective name for a series of connected lakes separated by innumerable bays, peninsulas, and islands with highly irregular shapes. It has therefore a relative long shoreline of over 5,600 km (excluding islands) compared to its surface area of 1,570 km². It is the source of the Saint-Maurice River.