The "arrondissement" of Montmorillon is in southern Vienne and is bordered to the north by the other two "arrondissements" of the departmentː Poitiers to the nortwest and Châtellerault to the northeast. The "arrondissement" is also surrounded by the Indre department to the east, the Haute-Vienne department to the southeast, the Charente to the south and the Deux-Sèvres department to the west.