Whilst Bishop of Lyons, from A.D.177 to 202, he employed the five and twenty years in propagating the Christian faith in Gaul, and in defending, by his writings, the Christian doctrines against the discord to which they had already been subjected in the East, and which was beginning to penetrate to the West.

In 202, during the persecution instituted by Septimius Severus, St.Irenaeus crowned by martyrdom his active and influential life.

It was in his episcopate that there began what may be called the swarm of Christian missionaries who, towards the end of the second and during the third centuries, spread over the whole of Gaul, preaching the faith and forming churches.

Some went from Lyons at the instigation of St.Irenaeus; others from Rome, especially under the pontificate of Pope St.Fabian, himself martyred in 219; St.Felix and St.Fortunatus to Valence, St.Ferreol to Besancon, St.Marcellus to Chalons-sur-Saone, St.Benignus to Dijon, St.Trophimus to Arles, St.Paul to Narbonne, St.Saturninus to Toulouse, St.Martial to Limoges, St.Andeol and St.Privatus to the Cevennes, St.Austremoine to Clermont-Ferrand, St.Gatian to Tours, St.Denis to Paris, and so many others that their names are scarcely known beyond the pages of erudite historians, or the very spots where they preached, struggled, and conquered, often at the price of their lives.

Such were the founders of the faith and of the Christian Church in France.