Rochefort is in the northern half of the department. It is bordered to the north by the "arrondissement" of La Rochelle, to the northeast by the Deux-Sèvres department, to the east by the "arrondissements" of Saint-Jean-d'Angély and Saintes. To the south is the upper part the Gironde estuary, the largest estuary of France, and the Atlantic Ocean is to the west.