Cyril of Alexandria (c. 376 – 444) is the Patriarch of Alexandria from 412 to 444.

He comes to power when the city is at its height of influence and power within the Roman Empire.

Cyril writes extensively and is a leading protagonist in the Christological controversies of the later 4th and 5th centuries.

He is a central figure in the First Council of Ephesus in 431, which leads to the deposition of Nestorius as Patriarch of Constantinople.

Cyril is counted among the Church Fathers and the Doctors of the Church, and his reputation within the Christian world has resulted in his titles Pillar of Faith and Seal of all the Fathers, but Theodosius II, the Roman Emperor, condemns him for behaving like a "proud pharaoh", and the Nestorian bishops at the Council of Ephesus declare him a heretic, labeling him as a "monster, born and educated for the destruction of the church."

(Edward Gibbon, Decline and Fall of the Roman Empire, 47) Cyril is well-known due to his dispute with Nestorius and his supporter Patriarch John of Antioch, whom Cyril had excluded from the Council of Ephesus for arriving late.

He is also known for his involvement in the expulsion of Novatians and Jews from Alexandria and the murder of the Hellenistic philosopher Hypatia by Coptic monks.

Historians disagree over the extent of his responsibility for these events.

The Roman Catholic Church does not commemorate Saint Cyril in the Tridentine Calendar: it added his feast only in 1882, assigning to it the date of 9 February.

The 1969 revision moved it to 27 June, considered to be the day of the saint's death, as celebrated by the Coptic Orthodox Church.

The same date has been chosen for the Lutheran calendar.

The Eastern Orthodox Church and Eastern Catholic Church celebrate his feast day on 9 June and also, together with Pope Athanasius I of Alexandria, on 18 January.