two ecumenical councils of the Christian church, held at Nicaea (now İznik, Turkey), a city of ancient Bithynia, in Asia Minor.

First Council of Nicaea.

Held in 325, this first ecumenical council was convened by Constantine I, emperor of Rome, to settle the Arian dispute concerning the nature of Jesus Christ (see ARIANISM,). Of the 1800 bishops in the Roman Empire, 318 attended the council. The Nicene Creed, which defined the Son as consubstantial with the Father, was adopted as the official position of the church regarding the divinity of Christ. The council also fixed the celebration of Easter on the Sunday after the Jewish Pesach, or Passover, and granted to the bishop of Alexandria, Egypt, authority in the East in the fashion of Rome’s quasi-patriarchal authority, which was not, as sometimes erroneously stated, the same as that of the pope. In this granting of authority lay the origin of the patriarchates throughout the church.

Second Council of Nicaea.

Held in 787, the second of the councils at Nicaea was the seventh ecumenical council. It was convened by Irene, empress of the East, and attended by 350 bishops, the majority of whom were Byzantine. In spite of strong objections by the iconoclasts, the council validated the veneration of images and ordered their restoration in churches throughout the Roman Empire.