MAMERTO, bishop of VIENNE, saint. - He is commemorated on 11 May. Nothing is known of his life before he became bishop. He was already governing the Church of Vienne in 463, when Pope Ilaro had to write to Leonzio, bishop of Arles, requesting that the question of the ordination of the bishop of Die by M. be examined at the annual Synod of Gaul, since he had usurped a right belonging to the see of Arles.
In this letter and in another which the same Pope wrote to the bishops of Gaul, M. is described as ambitious, intemperate, proud, rebellious against papal provisions, and threatened with deposition. Sidonio Apollinare, however,
Avito and St Gregory of Tours praise him as a man of irreproachable morals, holy life, and zeal for the good of souls. M. has remained famous in the history of the Church because in 474 he instituted the Rogations (v.) in order to propitiate God on account of the calamities afflicting his Church. M. died in 475; he was buried in the church of the Apostles outside the walls.