Lac du Bourget, Natural lake in Savoie, France
Lac du Bourget is a lake in Savoie, at the southern end of the Jura Mountains, 18 km long and 1.6 to 3.5 km wide, with an average depth of 85 m and a maximum of 145 m. It is the deepest lake lying entirely within France and the largest natural lake of glacial origin in the country. Its shores are formed by the Mont du Chat and the Chaîne de l'Épine to the west and the Bauges to the east.
The water body formed during the Würm glaciation when glaciers shaped the land and retreated. These geological processes created a basin that later filled with water.
Poet Alphonse de Lamartine spent time along the shores and dedicated several poems to the water. His verses helped bring this region into French literary tradition.
Fourteen ports around the shore offer more than 2,600 berths for sailing boats and provide access to water sports. Activities such as kayaking, rowing, and wakeboarding are available at different locations.
The bezoule, a small freshwater fish, was found only in Lac du Bourget and is now extinct. The lake has been a Ramsar wetland site, and in 2025 UNESCO designated it a biosphere reserve. Its meromictic deep water does not mix with surface layers each year.
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