Saint Athanasius of Alexandria (Greek: θανάσιος Ἀλεξανδρείας, Athanásios Alexandrías), also called Athanasius the Great, Athanasius the Confessor or, primarily in the Coptic Orthodox Church, Athanasius the Apostolic, was the twentieth bishop of Alexandria (as Athanasius I). His episcopate lasted 45 years (c. June 8, 328 - May 2, 373), of which over 17 were spent in five exiles ordered by four different Roman emperors. Athanasius was a Christian theologian, a Church Father, the chief defender of Trinitarianism against Arianism, and a noted Egyptian leader of the fourth century.
Conflict with Arius and Arianism as well as successive Roman emperors shaped Athanasius' career. In 325, at the age of 27, Athanasius began his leading role against the Arians as a deacon and assistant to Bishop Alexander of Alexandria during the First Council of Nie.ea. Roman emperor Constantine the Great had convened the council in May-August 325 to address the Arian position that the Son of God, Jesus of Nazareth, is of a distinct substance from the Father. Three years after that council, Athanasius succeeded his mentor as archbishop of Alexandria. In addition to the conflict with the Arians (including powerful and influential Arian churchmen led by Eusebius of Nicomedia), he struggled against the Emperors Constantine, Constantius II, Julian the Apostate and Valens. He was known as "Athanasius Contra Mundum" (Latin for Athanasius Against the World).
Nonetheless, within a few years after his death, Gregory of Nazianzus called him the "Pillar of the Church". His writings were well regarded by all Church fathers who followed, in both the West and the East, who noted their rich devotion to the Word-become-man, great pastoral concern, and profound interest in monasticism. Athanasius is counted as one of the four great Eastern Doctors of the Church in the Roman Catholic Church. In the Eastern Orthodox Church, he is labeled as the "Father of Orthodoxy". Some Protestants label him as "Father of the Canon". St. Athanasius is often shown as a bishop arguing with a pagan, a bishop holding an open book or a bishop standing over a defeated heretic. He is a patron saint of theologians, and faithful Orthodox and Roman Catholic Christians and hailed to this day as a great Defender of the Faith. His feast day is celebrated on May 2.
- taken from: wikipedia & catholic.org