Arcachon is a commune in the southwestern French department of Gironde. It is a popular seaside resort on the Atlantic coast 55 kilometres (34 mi) southwest of Bordeaux, in the Landes forest. It has a sandy beach and a mild climate said to be favourable for invalids suffering from pulmonary complaints.

Gironde is the largest department in the Nouvelle-Aquitaine region of Southwestern France. Named after the Gironde estuary, a major waterway, its prefecture is Bordeaux. In 2019, it had a population of 1,623,749. The famous Bordeaux wine region is in Gironde. It has six arrondissements, making it one of the departments with the most arrondissements.