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Léman was the name of a département of the First French Empire. Its name is 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 départements Mont-Blanc (northern Savoy) and Ain (around Gex).

The capital of Léman département was Geneva. The département was subdivided into the arrondissements of Geneva, Bonneville and Thonon-les-Bains. Its territory corresponds with the present Swiss canton of Geneva and parts of the present French départements Ain and Haute-Savoie.

After the final defeat of Napoleon Bonaparte 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 Ain département.