Avitus was probably born at Vienne, for he was baptized by bishop Mamertus. About 490 he was ordained bishop of Vienne. In 499 Vienne was captured by Gundobad, king of the Burgundians, who was at war with Clovis, king of the Franks, where he came to the attention of that king. Avitus, as metropolitan of southern and eastern Gaul, took the lead in a conference between the Catholic and Arian bishops held in presence of Gundobad at Sardiniacum near Lyons. He won the confidence of King Gundobad, and converted his son, King Sigismund to Catholicism.