Bishop of Arles, was born in Gaul at the beginning of the fifth century. Belonging to a family of distinction, he received a good education and gave early proof of ability and perseverance. Through the influence of Honoratus, abbot of Lerins, he became a monk; and after some strong opposition on his part, he consented to become bishop of Arles, at the early age of 29. The part which he took in the deposition of Chelidonius involved him in a quarrel with Leo the Great. Both Hilary and Cheldonius betook themselves to Rome, but Hilary, though willing to consult Leo, was not willing to submit to his authority. This at once provoked the hostility of the Pontiff. The deposition of Cheldonius was cancelled, and Hilary was obliged to make his escape, as best he could, back to Gaul. After being deprived of his authority by Leo, the well-known edict of Valentinian III. decreed, "Ut Episcopis Galli-canis omnibusque pro lege esset quidquid apostolicae sedis auctoritas sanxisset, &c." This encroachment upon Gallican ecclesiastical liberty is important in the controversy between Romanists and Protestants, as showing, first, that about the middle of the 5th century supreme power was claimed by the Roman Pontiff; and, secondly, that this claim was resisted by the metropolitan of Gaul. Hilary died A.D. 449, 49 years of age. He wrote numerous epistles, of which that addressed to Eucherius is extant. We have also his life of Honoratus his preceptor.

St., Bishop of Poitiers, was born in Sardinia in the middle of the 4th century. He and Lucifer of Cagliari appeared at the Council of Milan before Constantius, to defend the followers of Athanasius. His remarks offended the emperor so much that he was ordered to be scourged and sent into banishment. He held that all heretics, including Arians, should be re-baptized before admission to the Catholic Church. Some writings ascribed to him are probably not his.

St., Bishop of Arles, was born in the same town at the beginning of the 4th century. His parents were pagans of distinction, who afforded him every means of acquiring a good education. He was particularly struck with the writings of Moses, and afterwards with the gospels. He became a Christian, and was baptized along with his wife and daughter. He was greatly respected in his native city, and, although married, he was chosen bishop. This took place at the middle of the 4th century. At this period Arianism was spreading rapidly through the Western Church, and he set himself to oppose it. With this view he obtained the excommunication of Saturninus, bishop of Arles. But by the Council of Beziers, A.D. 356, he was banished to Phrygia. In 359 he made his appearance at the convocation of bishops at Sileucia in Isauria, and energetically resisted the opponents of the consubstantiality of the Word. Thereafter, at Constantinople, he was so persevering against the prevailing Arianism of the court, that he was sent back to his bishopric at Poitiers. Though he was received in triumph, he had enough to do for some time in eradicating the Arianism which had sprung up during his absence. After expelling Saturninus a second time, he accused Auxentius, bishop of Milan, of holding erroneous views. Both were summoned before the emperor Valentinian. Auxentius gave satisfactory answers. Hilary declared him a hypocrite, and was ordered to leave Milan as a disturber of the peace of the church. He died in January 368. His great energy of character, his courage and unwearied perseverance rendered him very influential during his life. His zeal, however, was often injudicious. He was called the hammer of the Arians (Malteus Arianaorum), from his determined opposition to the Arian heresy. Of his works, his Commentary on Matthew is the oldest extant on that evangelist. His most elaborate work consists of twelve books on the Trinitarian controversy. He wrote several books addressed to the Emperor Constantius in favour of the Catholics against the persecutions of the Arians; he wrote also several epistles still extant, and some poems have been ascribed to him. The best edition of his works is that of Constant, reprinted by Scipio Maffei, 1730. 2 vols. folio.