Castel San Vincenzo is a comune in the Province of Isernia in the Italian region Molise, located about 50 kilometres west of Campobasso and about 15 kilometres northwest of Isernia. The Abbey of San Vincenzo al Volturno is located in its territory. It is also home to an artificial lake, created in the 1950s for a hydroelectric plant. Castel San Vincenzo borders the following municipalities: Cerro al Volturno, Montenero Val Cocchiara, Pizzone, Rocchetta a Volturno, San Biagio Saracinisco.