ALERIA, Diocese of. – An ancient bishopric of Corsica, which took its name from an ancient city, already a Phocaean colony, situated on the banks of the Tavignano. The existence of the diocese in 591 is attested by a statement of St Gregory the Great. Initially subject to the immediate jurisdiction of the Pope, the ancient bishopric passed, in the 11th century, to that of Pisa (see Ajaccio). In the 16th century, the bishops of A. established their residence at Bastia, then at Cervione, Campoloco, and Corte.
According to Matteo di Flentin, at the end of the 17th century, the church of St Erasmus in Cervione served as the cathedral of A., which had been destroyed, and the diocese consisted of 18 pieve and 3 parishes. Among its ancient bishops were notable figures such as Gian Andrea Bussi (1466–75; see), Ardicino della Porta (1475–93) and above all St Alexander Sauli (1570–91; see), who may be considered its second founder. The last bishop of A. was Giovanni Giuseppe Maria de Guernes (6 Aug. 1770?), since the Concordat of 1801 reduced the bishops of Corsica to one, with its see at Ajaccio.