Chablais (from the Latin caput lacus "head of Lake Geneva"; Italian Chiablese; usually with article) is the area south of Lake Geneva.

The larger western part – the lakeshore around the towns of Thonon-les-Bains and Évian-les-Bains and the catchment area of the river Dranse – belongs to the French department of Haute-Savoie. The Swiss part through which the Rhone flows consists of the Valais district of Monthey and the Vaud district of Aigle.

Geographically, the Chablais belongs to the Savoy, Fribourg and Bernese Alps. At 3258 m above sea level, the Haute Cime of the Dents du Midi in the Valais part of the Savoy Alps is the highest elevation.

The French part of the Chablais has been designated as a UNESCO Global Geopark by UNESCO since 2012 under the brand name Geopark Chablais.