Ancient Diocese of Saint-Malo
The former Breton and French Catholic Diocese of Saint-Malo (, then ) 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.