ARCACHON, town and bathing-resort, south-west France, in the department of Gironde, 37m. W.S.W. of Bordeaux on the Southern railway. Pop. (1931) 12,529. It is situated on the south shore of a large bay, the Bassin d'Arcachon, at the foot of pine-clad dunes. The summer town, extending for 21m. along the shore, has a sandy beach, frequented by bathers; the winter town, farther inland, is a climatic station among the pine woods.