Lac du Bourget, France’s largest natural glacial lake, stands as a beacon of ecological preservation and sustainable tourism. Nestled between the Bauges massif and Épine mountain range in Savoie, this sapphire-hued gem has undergone decades of environmental rehabilitation to become one of Europe’s cleanest lakes. From pioneering wastewater management initiatives to biodiversity conservation and eco-conscious tourism, Lac du Bourget exemplifies how nature and human activity can coexist harmoniously. This article explores its ecological strengths, sustainability efforts, must-visit destinations, and its role as a model for future environmental stewardship.