Diocese in Piedmont, Italy, a suffragan of Vercelli. It was made a see in 1175 by Alexander III, by a Brief of 30 January, 1176, in which he declares that he selects a bishop without any detriment to the rights of the chapter for the future. It was suppressed in 1213, and united to Acqui, 1405; suppressed, 1803, and re-established as independent in 1817. It was vacant from 1854 to 1867. There are 116,000 Catholics; 61 parishes, 143 secular priests, and 188 churches and chapels.
Battandier, Ann. pontif. cath. (1906).