Eutychius ( 512 – 5 April 582), considered a saint in the Catholic and Orthodox Christian traditions, was the Ecumenical Patriarch of Constantinople from 552 to 565, and from 577 to 582. His feast is kept by the Orthodox Church on 6 April, and he is mentioned in the Catholic Church's "Corpus Juris". His terms of office, occurring during the reign of Emperor Justinian the Great, were marked by controversies with both imperial and papal authority.