Les Appalaches (French pronunciation: [lez‿apalaʃ]) is a regional county municipality (RCM) in the Chaudière-Appalaches region in southeastern Quebec, Canada.

It was established in 1982 from parts of the historic counties of Beauce, Frontenac, Mégantic, and Wolfe.

The county seat and largest city is Thetford Mines.

The name of the RCM is linked to its location in the Appalachian Mountains with Mounts Adstock, Caribou, Oak, and Saint-Adrien being the highest.

Mother tongue from Canada 2016 Census[3] Highways and numbered routes that run through the municipality, including external routes that start or finish at the county border:[5]