Dionysus Of Alexandria, a saint and bishop of the church, born in Alexandria, Egypt, late in. the 2d century, died there A. D. 265. He was of a noble and wealthy pagan family, but in the course of his early philosophical studies his attention was turned to the Christian sacred writings, especially the epistles of Paul, and he became a convert. He left the heathen schools, became a pupil of Origen, was ordained priest, and about 232 was chosen to succeed Heraclas as chief of the Alexandrian school of theology. About 247 he was raised to the office of bishop, made vacant by the death of Heraclas. Shortly after this violent persecutions broke out against the Christians. The populace of Alexandria had been stirred up against them by a heathen prophet, and the edict of Decius, which reached that city in 250, put arms in the hands of their enraged enemies. Dionysius, who had taken an active part in preparing the Christians for the coming trial, was arrested, sent to be put to death, rescued by a band of peasants, and remained concealed more than a year in the Libyan desert, sending continual messages meanwhile to his brethren in the city. In the persecution under Valerian in 257, Dionysius was again exiled from his see.

After his restoration (260), brought about by an edict of Gallienus favorable to the Christians, he was more than once called to mediate on occasions of public strife. - The writings of Dionysius were numerous, but most of them have been lost. They were mainly controversial. He wrote two books refuting the theory of Nepos, of the millennial earthly reign of the Saviour. In opposition to Sabellius, who denied the distinct personality of the members of the Trinity, he wrote several books and epistles, caused the heresy to be condemned by a council, and insisted upon the distinction between the Son and the Father so strongly that it brought upon him the charge of denying the divinity of Christ, against which he defended himself. He also defended the doctrine of the divinity of the Holy Spirit. In opposition to Paul of Samosata, Dionysius maintained the consubstantial nature of the Son and the Father. The fragments of his writings were collected by Simon de Magistris (folio, Rome, 1796), and are also contained in the Bibliotheca Patrum, vol. iii.