Saint Irenaeus, one of the fathers of the church, supposed to have been born near Smyrna about 135, died in Lyons about 202. In a letter to the Valentinian Florinus, Irenaeus reminds him of their having been both disciples of Polycarp; he also studied under Papias, according to Jerome. He probably accompanied Pothinus into Gaul, was ordained priest by him, and labored under him among the Greek colonists on the Rhone. In the beginning of 177 he was sent to Rome by the church of Lyons and Vienne, to consult with Pope Eleuthe-rus about the spread of the Montanistic doctrines, and was while there elected and consecrated bishop of Lyons. In the controversy relating to the celebration of Easter, Irenaeus acted as mediator between the eastern bishops and Pope Victor I. About 181 he published in five books his work Adversus Hoereses, which is considered the most valuable relic of early patristic literature. Of the original Greek, only the greater part of the first book has been preserved in the writings of Epiphanius and of Hippolytus, who was a pupil of Irenaeus; but the existing Latin version, in five books, is very ancient, and perhaps contemporary with the author.

Four Greek fragments of other compositions attributed to him were discovered by Pfaff at Turin in 1715. The first edition of his works is that of Erasmus (Basel, 1526, frequently republished); the best are those of Grabe (Oxford, 1702), Massuet (Paris, 1710, and Venice, 1734), Stieren (Leipsic, 1851-'3), Harvey (Cambridge, 1857), and in vol. vii. of Migne's Patrologie grecque.