Dionysius of Alexandria was the Bishop of Alexandria during the middle of the third century. A convert to Christianity at a mature age, he led the Alexandrian Catechetical School before becoming the bishop of Alexandria. He was called Dionysius the Great by Eusebius of Caesarea, St. Basil the Great, and others. His feast day is October 5.
Much of the information about his life comes from the extensive correspondence he maintained during his life that survived in the works of Eusebius. Dionysius was born about the year 190 in Alexandria. He was born into pagan family of wealth. He was well read. He studied indepth the traditions of the heretic before becoming a Christian at a mature age. Dionysius joined the Catechetical School of Alexandria where he became a student of Origen and Heraklas. In 232, as Heraklas became the Bishop of Alexandria, Dionysius, now a priest, succeeded him as leader of the school.
In 248, Dionysius succeeded Heraklas as Bishop of Alexandria, apparently also keeping his position as head the Catechetical School. In 249, a riot against Christians arose in Alexandria, nurtured by a popular pagan prophet and poet, during which Christians were at risk from mobs. Soon, the riots became legal persecutions instituted by the new Emperor Decius. The Christians were subjected to all kinds of cruelty, tortures of all sorts, all aimed to drive the victim Christians to sacrifice to the gods. Many martyrs were made. Many also fled to the deserts. Dionysius joined those who fled, but was identified and made prisoner. News of Dionysius' capture soon became known to a party of Christians who descended on the soldiers, holding him, who took flight. Dionysius remained in the desert until the persecutions stopped in 251.
As the persecutions ended Dionysius was confronted by a request for support by Novation in his attempt to obtain the see of Rome over the newly elected Cornelius. Dionysius did not give him any support, and, indeed, asked for Novation retirement. In regard the controversies of the time concerning readmission of Christians to communion who had lapsed during the persecutions, Dionysius took the side that they should not be permanently excluded but should be remitted after due penitence and without re-baptism.
Another controversy in which Dionysius took part was that concerning the issue raised by the Millenarians who believed that Jesus Christ would return and establish a kingdom on Earth for 1,000 years. The belief in Chiliasm, as the belief was called, was denounced strongly by Dionysius. During the heretical debates Dionysius used language that made Jesus not as divine as the father, a position about which he quickly corrected himself. About the year 250 he further affirmed his position of the essence of Christ with the use of the title "Theotokos" for the Virgin Mary in correspondence to Paul of Samosata, a title first used by Origen in 230.
Dionysius reposed on November 17, 265.