The Diocese of Ajaccio is a Latin Church ecclesiastical jurisdiction or diocese of the Catholic Church in France. The diocese comprises the whole of the island of Corsica.

Ajaccio Cathedral, officially the Cathedral of Our Lady of the Assumption of Ajaccio and also known as the Cathedral of the Assumption of Saint Mary, is a Roman Catholic church located in Ajaccio, Corsica. The cathedral is the ecclesiastical seat of the Bishop of Ajaccio, a suffragan of the Archdiocese of Marseille. It is dedicated to the Virgin Mary, and is in the Baroque/Mannerist architectural style.