Léman (French: [lemɑ̃]) was a department of the First French Empire. Its name comes from the French name of Lake Geneva, Lac Léman. It was formed in 1798, when the republic of Geneva was occupied by the French. Léman also included districts that were previously part of the departments of Mont-Blanc (northern Savoy) and Ain (around Gex). Its territory corresponded with the present Swiss canton of Geneva and parts of the present French departments of Ain and Haute-Savoie.
- Geneva, cantons: Carouge, Chêne-Thônex, Collonge, Frangy, Geneva (3 cantons), Gex, Reignier and Saint-Julien.
- Bonneville, cantons: Bonneville, Chamonix, Cluses, Megève, La Roche, Sallanches, Samoëns, Taninges and Viuz-en-Sallaz.
- Thonon, cantons: Douvaine, Évian, Saint-Jean-d'Aulps and Thonon.
Its population, in 1812, was 210,478 and its area was 280,000 hectares.
After the final defeat of Napoleon in 1815, the former republic of Geneva became a Swiss canton, and Savoy was returned to the Kingdom of Sardinia. The area around Gex returned to the department of Ain.