St., a bishop of Lyons, was born in Greece about the year 120. He was the disciple of Papias and St Polycarp, by whom, it is said, he was sent into Gaul in 157. He lived at Lyons, where he performed the office of a priest; and in 178 was sent to Rome, where he disputed with Valentius, and his two disciples Florinus and Blattus. At his return to Lyons, he succeeded Photinus, bishop of that city; and suffered martyrdom in 202, under the reign of Severus. He wrote many books in Greek, of which there only remains a barbarous Latin version of his five books against heretics, some Greek fragments in different authors, and Pope Victor's letter mentioned by Eusebius. The best editions of his works are those of Erasmus, in 1526; of Grabe, in 1702; and of Father Maffuet, in 1710.

He ought not to be confounded with St Irenaeus the deacon, who in 275 suffered martyrdom in Tuscany, under the reign of Aurelian; nor with St Irenaeus, bishop of Sirmium, who suffered martyrdom on the 25th of March 304, during the persecution of Diocletian and Maximianus.