Theophanes was the son of Isaac, the imperial governor of the islands of the Black Sea, and of Theodora, of whose family nothing is known. At the death of his father when he was only three, he was left the heir of a very large estate and was subsequently brought up at the court of the Byzantine Emperor Constantine V, who saw to his education.
He was induced to marry early, but convinced his wife to lead a life of virginity. Later, after the death of his father-in-law, they separated by mutual consent, each to embrace monastic life. Theophanes first entered Polychronius Monastery on Mount Sigriano, then went on to found another monastery on the island of Kalonymos, which was part of his inheritance.
Six years later, Theophanes returned to Sigriano where he made another monastic foundation. It was in virtue of his position as abbot of this monastery that he participated in the Second Council of Nicaea in 787, which issued the declaration of faith concerning the veneration of holy images:
“As the sacred and life-giving cross is everywhere set up as a symbol, so also should the images of Jesus Christ, the Virgin Mary, the holy angels, as well as those of the saints and other pious and holy men be embodied in the manufacture of sacred vessels, tapestries, vestments, etc., and exhibited on the walls of churches, in the homes, and in all conspicuous places, by the roadside and everywhere, to be revered by all who might see them. For the more they are contemplated, the more they move to fervent memory of their prototypes. Therefore, it is proper to accord to them a fervent and reverent adoration, not, however, the veritable worship which, according to our faith, belongs to the Divine Being alone — for the honor accorded to the image passes over to its prototype, and whoever adores the image adores in it the reality of what is there represented.”
When Emperor Leo the Armenian resumed his iconoclastic persecution, he had Theophanes brought to Constantinople. The Emperor tried in vain to induce him to condemn the same veneration of icons that had been sanctioned by the council. When the Emperor’s promises failed to move him, he resorted to threats. Finding the venerable old man equally unmoved, the Emperor submitted him to 300 lashes and had him thrown in a dungeon. His imprisonment lasted for two years, but he remained constant in his faith. Theophanes was released in 817 only to be banished to Samothrace, a Greek island in the Aegean Sea, where he died seventeen days later as a consequence of the cruel treatment he had endured during his imprisonment.
Theophanes left a chronicle or short history of the world to the year 813. He is also mentioned in the Roman Martyrology.