Ecumenical Council of Ephesus

The Council of Ephesus was a council of Christian bishops convened in Ephesus (near present-day Selçuk in Turkey) in AD 431 by the Roman Emperor Theodosius II. This third ecumenical council, an effort to attain consensus in the church through an assembly representing all of Christendom, confirmed the original Nicene Creed, and condemned the teachings of Nestorius, Patriarch of Constantinople, who held that the Virgin Mary may be called the Christotokos, "Birth Giver of Christ" but not the Theotokos, "Birth Giver of God". It met in June and July 431 at the Church of Mary in Ephesus in Anatolia.

Nestorius' doctrine, Nestorianism, which emphasized the distinction between Christ's human and divine natures and argued that Mary should be called Christotokos (Christ-bearer) but not Theotokos (God-bearer), had brought him into conflict with other church leaders, most notably Cyril, Patriarch of Alexandria. Nestorius himself had requested the Emperor to convene the council, hoping that it would prove his orthodoxy; the council in fact condemned his teachings 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 the Eastern Roman Emperor Theodosius II to call a council in which all grievances could be aired, hoping that he would be vindicated and Cyril condemned.