La Teste-de-Buch is a coastal commune in the Gironde department in the Nouvelle-Aquitaine region in Southwestern France. Until 13 June 1994, it was officially known simply as La Teste. The commune is located on the south shore of Arcachon Bay and on the Atlantic coast of France, lying in the southwestern part of Gironde, on the departmental border with Landes. It is the eighth-largest commune in metropolitan France in geographical area at 180.20 km2.