Hilary of Poitiers was Bishop of Poitiers and a Doctor of the Church. He was sometimes referred to as the "Hammer of the Arians" and the "Athanasius of the West". His name comes from the Latin word for happy or cheerful. In addition to his important work as bishop, Hilary was married and the father of Abra of Poitiers, a nun and saint who became known for her charity.

Hilary was born at Poitiers either at the end of the 3rd or beginning of the 4th century A.D. His parents were pagans of distinction. He studied the Old and New Testament writings and was baptized with his wife and daughter Abra.

The Christians of Poitiers so respected Hilary that about 350 or 353, they unanimously elected him their bishop. At that time Arianism threatened to overrun the Western Church. One of his first steps was to secure the excommunication of Saturninus, the Arian Bishop of Arles, and of Ursacius of Singidunum and Valens of Mursa, two of his prominent supporters.

About the same time, Hilary wrote to Emperor Constantius II a remonstrance against the persecutions by which the Arians had sought to crush their opponents. His efforts did not succeed at first, for at the synod of Biterrae, summoned by the emperor in 356 with the professed purpose of settling the longstanding dispute, an imperial rescript banished the new bishop, along with Rhodanus of Toulouse, to Phrygia. Hilary spent nearly four years in exile, although the reasons for this banishment remain obscure.

He continued to govern his diocese while in Phrygia and wrote two of the most important of his contributions to dogmatic and polemical theology: the De synodis or De fide Orientalium, an epistle addressed in 358 to the Semi-Arian bishops in Gaul, Germania and Britain, analyzing the views of the Eastern bishops on the Nicene controversy. In reviewing the professions of faith of the Oriental bishops in the Councils of Ancyra, Antioch, and Sirmium, he sought to show that sometimes the difference between certain doctrines and orthodox beliefs was rather in the words than in the ideas. This led to his counseling the bishops of the West to be more reserved in their condemnation.

Hilary also attended several synods during his time in exile, including the council at Seleucia (359). On returning to his diocese in 361, Hilary spent most of the first two or three years trying to persuade the local clergy that the homoion confession was merely a cover for traditional Arian subordinationism. In about 360 or 361, with Hilary's encouragement, Martin, the future bishop of Tours, founded a monastery at Ligugé in his diocese.

In 364, Hilary extended his efforts once more beyond Gaul. He impeached Auxentius, bishop of Milan, a man high in the imperial favour, as heterodox. Upon returning home, Hilary published the Contra Arianos vel Auxentium Mediolanensem liber in 365, describing his unsuccessful efforts against Auxentius. He also published the Contra Constantium Augustum liber, accusing the lately deceased emperor as having been the Antichrist, a rebel against God.

Hilary died in Poitiers in 367.

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