Theodore Studites, (born 759, Constantinople [now Istanbul, Tur.]—died Nov. 11, 826, Prinkipo, island in the Sea of Marmara; feast day November 11), abbot and leading opponent of iconoclasm, the doctrine opposing the veneration of religious images, which severely disturbed relations between the Byzantine and Roman churches.
Under the influence of his uncle, Abbot Plato of Symbola, later a saint, Theodore became a monk and, later, abbot of a monastery near Mount Olympus in Bithynia (northwestern Turkey). For opposing as adulterous the second marriage of the Byzantine emperor Constantine VI to his mistress Theodote in 795, Theodore was exiled to Thessalonica, Greece. After Constantine’s overthrow in 797, Theodore was recalled by the empress Irene. Thereafter, his religious community moved to the monastery of Studios in Constantinople. In 806 he clashed with the emperor Nicephorus I (who asserted authority over the Eastern church) about the appointment of Patriarch Nicephorus of Constantinople. Theodore was condemned by a council and exiled a second time (809–811).
When iconoclasm was revived by the emperor Leo V, Theodore led the opposition against the iconoclasts and was again exiled (816–820). Recalled by the emperor Michael II, who nevertheless favoured the iconoclastic party, Theodore was not allowed to resume his abbacy. With his monks he spent the rest of his life near Constantinople. He had fought for church independence from imperial power; because the patriarchs of Constantinople often had to compromise with the Byzantine emperors, he opposed the patriarchs too.
Most of his works—which include homilies, three polemical treatises against the Iconoclasts, and nearly 600 letters—are in J.-P. Migne, Patrologia Graeca (“Greek Fathers”), vol. 99 (1903).