Mamertus was Bishop of Vienne in Gaul. He and his brother, the theologian Claudianus Mamertus, were well educated, probably from a wealthy family near Lyons. Mamertus seems to have been married before he became bishop, shortly before 462. He ordained his brother a priest to help him.

In 463 he overstepped his authority by consecrating a bishop for Die, which belonged to the province of Arles. A synod ruled against him, and Pope Hilary threatened to take away his remaining suffragan sees. He seems to have submitted, since nothing more is heard of the dispute.

He moved the newly found relics of St Ferreolus to a church in Vienne. He is best remembered as the founder of the Rogation processions, the days of prayer and penance before Ascension. Sidonius Apollinaris is the witness for this.

Thin entry · the 1897 book gives only 161 words. We have not filled the gap with invented detail.

May ii.] S. Gengulf, turn away the plagues from us, and preserve us from all ill, from the pestilence, the hailstorm, the drought, the fury of our enemies; to give us favourable seasons, that our bodies may enjoy health, and our lands fertility, and that we may have peace and tranquillity, and obtain pardon for our sins.’7 Processions with litanies and psalms had been in use before, but never before fixed for the Rogation season. S. Mamertius built a church at Vienne in honour of S. Ferreolus the martyr. He was at the council of Arles in 475, and died probably in 477.

Bishop of Vienne, date of birth unknown; died shortly after 475. Concerning the life of Mamertus before his elevation to the See of Vienne, nothing certain is known. The fact that his brother, Claudianus Mamertus, the theological writer, received in his youth a sound training in rhetoric, and enjoyed the personal acquaintance of Bishop Eucherius of Lyons (434-50), suggests that the brothers belonged to a wealthy Gallic family from the neighbourhood of Lyons. Like his brother, St. Mamertus was distinguished for his knowledge of profane subjects as well as of theology, and, before his elevation to the episcopate, appears to have been married. His election and consecration took place shortly before 462. As bishop he enlisted the services of his brother, who had withdrawn to a cloister, and ordained him priest of Vienne. The activity of the brothers is described in a letter of Sidonius Apollinaris (Epist., IV, xi), another of whose letters (VII, i) is addressed to Bishop Mamertus. In 463 Mamertus was engaged in a dispute with Pope Hilarius on the question of the privileges of the Bishop of Arles. Pope Leo I had regulated the boundaries of the ecclesiastical provinces of Arles and Vienne: under the latter he left the Dioceses of Valence, Tarentaise, Geneva, and Grenoble, but all the other dioceses in this district were made subordinate to Arles. Regardless of this decision and infringing on the rights of his colleague of Arles, Mamertus consecrated in 463 a bishop for the city of Die (Dea). King Gundiac of Burgundy complained to Pope Hilary of this action, whereupon the latter wrote to Bishop Leontius of Arles on 10 Oct., 463, bidding him summon a synod of bishops from the different provinces to enquire into the matter. In a subsequent letter to the bishops of the provinces of Lyons, Vienne, Narbonnensis I and II, and Alpina, he also refers to the matter, and directs them to obey Leontius's summons to a regularly constituted synod (Thiel, "Epist. Rom. Pont.", I, cxlvi, cli; Jaffé, "Regesta Rom. Pont.", I, 2nd ed., dlvi, dlix). The synod decided against Mamertus, as we learn from another letter of the pope dated 25 February, 464 (Thiel, op. cit., I, cxlviii; Jaffé, op. cit., I, dlvii). In this Hilary declares that Mamertus and the bishop unlawfully consecrated by him should really be deposed; desiring, however that clemency be used, he commissioned Bishop Veranus to inform Mamertus that, if he did not recognize and submit to the regulations of Pope Leo, he would be deprived also of the four suffragan [a bishop under the authority of an archbishop] dioceses, still subject to Vienne. The bishop invalidly installed by Mamertus was to be confirmed in his office by Leontius, after which he might retain the bishopric. Mamertus evidently submitted, since we find no subsequent reference to the incident.

During his episcopate, the remains of St. Ferreolus were discovered, and were translated by Mamertus to a church in Vienne, built in honour of that holy martyr (Gregory of Tours [bishop and historian of the Franks (d. 594)], "De gloria mart.", II, ii). St. Mamertus was the founder of the Rogation Processions (see ROGATION DAYS), as we learn on the testimony of Sidonius Apollinaris (Epist., V, xiv; VII, i), and his second successor, Avitus ("Homilia de Rogat." in P. L., LIX, 289-94). In connexion with these intercessory processions, Mamertus summoned a synod at Vienne between 471 and 475. About 475 he attended a synod at Arles, which dealt with the predestination teaching of Lucidus, a Gallic priest. As this is the latest information we possess concerning him, we may assume that he died shortly afterwards. After his death he was venerated as a saint. His name stands in the "Martyrologium Hieronymianum" and in the "Martyrologium" of Florus of Lyons under 11 May, on which day his feast is still celebrated (Quentin, "Les martyrologes historiques", 348).

DUCHESNE, Fastes épiscopaux de l'ancienne Gaule, I (Paris, 1894), 147; HEFELE, Konziliengesch., II (2nd ed.), 580 sqq., 596, 597; Acta SS., II. 629 sq.; TILLEMONT, Mémoires pour servir à l'hist. eccl, XVI, 104; TERREBASSE, Notice sur le tombeau de St. Mamert récemment découvert dans l'église de St. Pierre à Vienne (Vienne, 1861).