Mark of Ephesus, known by the family name Eugenikos, was a fifteenth-century Byzantine hierarch and theologian remembered chiefly as the only member of the Orthodox delegation at the Council of Florence (1438–1439) who refused to sign the decree of union with the Church of Rome. For this stand he is honored in the Orthodox tradition with the title "Pillar of Orthodoxy," and his commemoration is kept on January 19.
By the accounts of his life, he was born in Constantinople, where his father served as a deacon and his family was of considerable means. Given the name Manuel at baptism, he received a thorough education, studying under teachers including George Gemistos Plethon, before being tonsured a monk with the name Mark. He lived the ascetic life on the Princes' Islands and at the Monastery of Saint George of Mangana in Constantinople, and was advanced to the metropolitan see of Ephesus shortly before the council.
Sent by the Emperor John VIII Palaiologos as part of the delegation seeking reunion with Rome—and, with it, Western military aid against the advancing Ottomans—Mark argued against the Latin doctrines of the Filioque, papal primacy, and a purgatorial fire. When the rest of the delegation signed the Tomos of Union, he alone withheld his signature. He spent his remaining years opposing the union, urging the faithful of Constantinople to reject it, and according to his life was for a time arrested and held on the island of Lemnos. Sources differ on the year of his repose, which is given variously as 1444 and 1457.
