MARATONIO. — Bishop of Nicomedia, who lived in the 4th century and was elevated to that see by Macedonius of Constantinople (342–60), probably being deposed by the Acacian party together with him and others of the Homoiousian party. He initially pursued a military career, attached to the statistics office of the praetorian prefecture of Constantinople. He later became a deacon of Constantinople and devoted himself zealously to caring for the sick and the poor in the hospices. Under the influence of Eustathius of Sebaste, he embraced the monastic life and founded in Constantinople a monastery of monks that still existed around the middle of the 5th century.
M. was universally regarded as a good and pious man; but his Homoiousian opinions and his devotion to Macedonius meant that, once he had become bishop of Nicomedia, he was a most ardent persecutor of the orthodox. After the deposition and death of Macedonius, M., supporting him through his work, his money, and the prestige of his asceticism, exercised such influence within the “Macedonian” party that his followers were also called “Maratonians.”
Historians who, beginning in 380, make Macedonius the heresiarch of the Pneumatomachi and interpret in this sense the designation “Macedonians” commonly given to them around this time likewise present, more or less clearly, M. as the second leader of this heresy and seem similarly to interpret the designation “Maratonians” given in Constantinople to the “Macedonians.” But there is no evidence that M., any more than Macedonius himself, explicitly concerned himself with the question of the Holy Spirit. When, not long after 366, the Pneumatomachian opinions were certainly accepted by the colleagues of his group, such as Eustathius of Sebaste and Eleusius of Cyzicus (v. PNEUMATOMACHI), M. no longer appears in history.