Euphemius of Constantinople (died 515) was Ecumenical Patriarch of Constantinople (490–496). Theophanes calls him Euthymius. Prior to his appointment, Euphemius was a presbyter of Constantinople, administrator of a hospital for the poor at Neapolis, unsuspected of any Eutychian leanings, and is described as learned and very virtuous.
In 482, the Emperor Zeno had published a decree called the Henotikon, which forbade in the current theological discussions any other criterion but those of the Councils of First Council of Nicaea and First Council of Constantinople (ignoring the decrees of Chalcedon), carefully avoided speaking of Christ's two natures, and used ambiguous formulae that were meant to conciliate the Monophysites. Despite his efforts, the Henotikon really satisfied no one: Monophysites disliked it as much as the Orthodox. However, Acacius at Constantinople, Peter Mongus Patriarch of Alexandria, and Peter the Fuller Patriarch of Antioch had all signed it. Pope Felix III convened in 484 a Roman synod of sixty-seven bishops that condemned the emperor's decree, deposed and excommunicated Acacius, Peter Mongus, and Peter Fuller. Acacius retorted by striking the pope's name from his diptychs and persecuted Catholics at Constantinople. When he died, Fravitta, his successor, applied for recognition at Rome, but in vain, since he would not give up communion with Peter Mongus.
Euphemius immediately recognized the Council of Chalcedon, restored the pope's name to his diptychs, and broke with Peter Mongus, who died in October of the year of Euphemius's accession (490). By these acts, he showed his desire to heal the rift with Rome. Unfortunately, he still refused to erase the names of his two predecessors (Acacius and Fravitta) from the diptychs, where they appeared among the faithful departed. Pope Felix insisted that heretics and favourers of heresy should not be prayed for publicly; Euphemius repeated his attempts at reconciliation to Pope Gelasius I, but the problem of his predecessors remained; Euphemius could not remove their names from the diptychs without causing embarrassment or insult to those they had baptized and ordained. Gelasius allowed that in other circumstances he would have written to announce his election, but sourly observes that the custom existed only between bishops who were united in communion, and was not to be extended to those who, like Euphemius, preferred a strange alliance to that with St. Peter. As a mark of condescension Gelasius granted the canonical remedy to all who had been baptised and ordained by Acacius.