First Nicene Council

First Council of Nicaea
16th-century fresco depicting the Council of Nicaea
Date	20 May to 19 June, AD 325
Accepted by	Roman Catholicism Eastern Orthodox Church Oriental Orthodoxy Assyrian Church of the East
Next council	First Council of Constantinople
Convoked by	Emperor Constantine I
President	Hosius of Corduba (and Emperor Constantine)
Attendance	318 (traditional number) 250–318 (estimates) — only five from Western Church
Topics	Arianism, the nature of Christ, celebration of Passover (Easter), ordination of eunuchs, prohibition of kneeling on Sundays and from Easter to Pentecost, validity of baptism by heretics, lapsed Christians, sundry other matters.
Documents and statements	Original Nicene Creed, 20 canons, and a synodal epistle
Chronological list of Ecumenical councils

The First Council of Nicaea (/naɪˈsiːə/; Greek: Νίκαια [ˈni:kaɪja]) was a council of Christian bishops convened in the Bithynian city of Nicaea (now Iznik, Bursa province, Turkey) by the Roman Emperor Constantine I in AD 325. Constantine I organized the Council along the lines of the Roman Senate and presided over it, but did not cast any official vote.

This ecumenical council was the first effort to attain consensus in the Church through an assembly representing all of Christendom. Hosius of Corduba, who was probably one of the Papal legates, may have presided over its deliberations.

Its main accomplishments were settlement of the Christological issue of the divine nature of God the Son and his relationship to God the Father, the construction of the first part of the Nicene Creed, establishing uniform observance of the date of Easter, and promulgation of early canon law.