Diocese made up of 42 communes in the province of Cagliari, Archbishopric of Oristano, Italy. The two sees were united by Julius II in 1503. Christianity was possibly introduced into Sardinia by groups of the faithful, who were condemned to work in its mines [Philos., IX, 12; Catal. Liber., s.v. "Pontianus"; cf. Harnack, Die Mission, etc. (Leipzig, 1902), 502]. Gregory the Great alludes to the episcopal see of Ales (anciently Uselli), in his letter to Januarius of Cagliari in 591 (Jaffé, 1130). After this nothing is to be found about it until 1147, when the name of Bishop Rello appears in a diploma. The local traditions of Terralba have preserved the memory of a Bishop Mariano, who erected the cathedral about 1144. The diocese contains 42 parishes, 102 priests, 59,530 inhabitants.
Cappelletti, Le chiese d'Italia (Venice, 1866), XIII, 249; Gams, Series episcoporum Ecclesiae Catholicae (Ratisbon, 1873), 831; Vitale, Apparatus ad Annales Sardiniae (Cagliari, 1780); Matthei, Sardinia Sacra seu historia de episcopis Sardis (Rome, 1758); Martini, Storia ecclesiastica di Sardegna (Cagliari, 1839).