Ancient Diocese of Saint-Malo

The former Breton and French Catholic Diocese of Saint-Malo (Latin: Dioecesis Alethensis, then Dioecesis Macloviensis) existed from at least the 7th century until the French Revolution. Its seat was at Aleth up to some point in the 12th century, when it moved to Saint-Malo. Its territory extended over some of the modern departments of Ille-et-Vilaine, Côtes-d'Armor, and Morbihan. Until the 860s, it was often termed the bishopric of Poutrocoet.