St. Irenaeus was born in or near Smyrna c. 135-140. Polycarp was then bishop of that city, and from his childhood Irenaeus listened to his discourses and received his instructions. The profound impression made upon his mind proves that he was, if not a disciple, at least an assiduous and thoughtful listener of the aged Bishop, and he loved to appeal later on to his authority. Polycarp was not his only master, for Irenaeus often mentions Asiatic presbyters with whom he had conversed and whose teachings he relates.
We do not know the circumstances which led Irenaeus to leave Asia and go to Gaul, nor do we know when this transfer took place. What we have said only proves that at this time he had reached the age of manhood and his intellectual and religious formation was already completed. In 177 we find him in Lyons, as a priest in the church of which St. Pothinus was bishop. Afterwards, he was delegated by the martyrs of Lyons, most of whom were still in prison, to carry to Pope Eleutherus a letter concerning the Montanistic troubles. He was furnished with a letter of recommendation, in which the martyrs styled him “one zealous for the Testament of Christ.” It was perhaps owing to this journey that Irenaeus escaped the fury of the persecutors. In 177 or 178 he was made bishop of Lyons, succeeding St. Pothinus. Three circumstances relative to his activities as a bishop are known: he combated the Gnostics, he labored in the evangelization of the country about Lyons, he interceded (c. 190-191) with Pope Victor I in the question of the Paschal observance, in order to preserve peace between the Church of Rome and the churches of Asia. It is commonly thought that he died in 202-203. The Church honors him as a martyr. St. Jerome is the first to give him this title in his commentary on Isaias, written between 408-410, and this is astonishing. However, the silence of ancient authors may be explained by the small notice which would be taken of the violent death of Irenaeus if he had been put to death under Septimus Severus in the general massacre of the Christians of Lyons.
(From A Handbook of Patrology by J. Tixeront, D.D., 1920 English edition)