Lac de Grand-Lieu
General data
- Name: Lac de Grand-Lieu
- Water system: Loire
- Water type: Natural lake
- Progression: Acheneau -> Loire -> Bay of Biscay -> Atlantic Ocean -> Planet Earth
- Climates: Temperate
- Continents: Europe
- Countries: France
Lac de Grand-Lieu is a lake located to the southwest of Nantes, in the Loire-Atlantique, France, and almost entirely in Saint-Philbert-de-Grand-Lieu. At an elevation of 5 m (16 ft), its surface area is 62.92 km2 (24.29 sq mi), making it the largest lake in France in winter, but second after Lac du Bourget in summer.
The lake is classified as a Local Nature Reserve, and use of boats on the lake are prohibited for all but a small number of licensed professional fishermen.