Key Facts:

Date 20 May-25 July 325
Location Nicaea
Number of Participants 250-300
Summoned by Constantine
Chaired by Ossius of Cordova
Key Participants Ossius of Cordova, Eusebius of Caesarea, Eusebius of Nicomedia, Alexander of Alexandria, Arius
Key Issues Arianism, Meletians, and the date of Easter
Key Events The following were excommunicated: Arius, Secundus of Ptolemais and Theonas of Marmarica
Ancient Descriptions Socrates, HE 1.8-13; Sozomen, HE 1.17-24; Theodoret, HE 1.7.1-9, 18; Anonymous, HE 2.5-11, 25-35; Eusebius LoC 3.4-24; Rufinus, HE 10.3ff; Jerome Dial. con. Luciferanus 20(18), 183; Philostorgius, HE 1.7-10; Athanasius, de Decretis, de Synodis, ad Afros. 

Surviving Documents:

Constantine’s Summons to the Council


Eusebius’ Letter to his Congregation

Canons (Greek and Latin/English)

The Council’s Letter to the Church in Egypt

Constantine’s Letter to the Church of Alexandria

Constantine’s Letter concerning the Date of Easter


Hanson, R.P.C. The Search for the Christian Doctrine of God (New York: T&T Clark, 1988) pp. 152-163.

Kannengiesser, C. “Nicaea” in The Encyclopedia of the Early Church (New York: Oxford University Press, 1992).

Created by JCB and PSAM

Last updated: 3-21-2023

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