Commemoration Day: May 29 (June 11) [Greek]
Biography
Bishop of the Church of Alexandria, the 19th Pope of Alexandria from 313 until his death. He took an active part in the theological disputes of his time: on the date of Easter, on the actions of Meletius of Lycopolis, and in the struggle against Arianism. He led the opposition to Arianism at the First Ecumenical Council in 325, at which he presided.
He was the teacher of his successor on the see, Athanasius of Alexandria.