Fort Louvois, which is known locally as Fort du Chapus, is a fortification built between 1691 and 1694, during the reign of Louis XIV, on the Chapus islet, and is about off shore in the town of Bourcefranc-le-Chapus in the department of Charente-Maritime, France. The fort sits opposite the citadel of Château d'Oléron on the island of Oléron. The fort was positioned so that a crossfire from the château and the fort would control the Pertuis de Maumusson (Passage of Maumusson) and impede access to the Rochefort roads from the south. Fort Louvois only saw action towards the end of World War II when bombardment greatly damaged the fort, necessitating later restoration.