Lac de Grand Maison, Artificial reservoir in Vaujany, France.

Lac de Grand Maison is an artificial reservoir in the French Alps that stretches between the communes of Vaujany in Isère and Saint-Colomban-des-Villards in Savoie. The basin sits at approximately 1,700 meters elevation and is surrounded by several walking trails that offer different views of the water and surrounding mountain landscape.

The Grand'Maison Dam was built between 1978 and 1985, creating the reservoir as the upper basin of a pumped-storage hydroelectric scheme. Water released through the turbines is pumped back up from a lower reservoir when demand is low, so the lake is refilled rather than fed by a single inflowing river.

The lake's name comes from the Grand'Maison dam and the hamlet it displaced; the reservoir lies below the Col du Glandon, a pass long used to cross between the Belledonne and Grandes Rousses ranges. The road along the shore is the D526, and the two white trailers parked beside it belong to EDF's hydroelectric operation.

The lake lies below the Col du Glandon, between the Belledonne and Grandes Rousses ranges, and is reached by a paved road that curves along its lower shore, where vehicles and white trailers park beside the water. The shoreline is bare rock and gravel, so the water's edge shifts with the reservoir level.

The water level changes noticeably throughout the year as EDF manages the reservoir for power generation and water storage. Visitors often notice the shoreline varies dramatically, sometimes revealing different views of the landscape depending on the season.