First Council of Ephesus

The First Council of Ephesus was the third ecumenical council of the early Christian Church, held in 431 at the Church of Mary in Ephesus, Asia Minor. The council was called amid a dispute over the teachings of Nestorius, Patriarch of Constantinople. Nestorius' doctrine, Nestorianism, which emphasized the disunity between Christ's human and divine natures, had brought him into conflict with other church leaders, most notably Cyril, Patriarch of Alexandria. Nestorius himself had requested that the Emperor convene council, hoping to prove his orthodoxy, but in the end his teachings were condemned by the council as heresy. The council declared Mary as Theotokos (God-bearer).

Nestorius' dispute with Cyril had led the latter to seek validation from Pope Celestine I, who authorized Cyril to request that Nestorius recant his position or face excommunication. Nestorius pleaded with Roman Emperor Theodosius II to call a council in which all grievances could be aired, hoping that he would be vindicated and Cyril condemned.

Approximately 250 bishops were present. The proceedings were conducted in a heated atmosphere of confrontation and recriminations and created severe tensions between Cyril and Theodosius. Nestorius was decisively outplayed by Cyril and removed from his see, and his teachings were officially anathematized. This precipitated the Nestorian Schism, by which churches supportive of Nestorius, especially in Persia, were severed from the rest of Christendom and became known as Nestorian Christianity, the Persian Church, or the Church of the East, whose present-day representatives are the Assyrian Church of the East, the Chaldean Syrian Church, the Ancient Church of the East, and the Chaldean Catholic Church. Nestorius himself retired to a monastery, always asserting his orthodoxy.

The council is accepted as the Third Ecumenical Council by Oriental Orthodox, Eastern Orthodox, Roman Catholics, and a number of other Western Christian groups.