The Council of Ephesus was a council of Christian bishops convened in Ephesus 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, "Christ-bearer" but not the Theotokos, "God-bearer". It met in June and July 431 at the Church of Mary in Ephesus in Anatolia.

Ephesus was a city in Ancient Greece on the coast of Ionia, 3 kilometres (1.9 mi) southwest of present-day Selçuk in İzmir Province, Turkey. It was built in the 10th century BC on the site of Apasa, the former Arzawan capital, by Attic and Ionian Greeks. During the Classical Greek era, it was one of twelve cities that were members of the Ionian League. The city came under the control of the Roman Republic in 129 BC.