27 June - Cyril of Alexandria, born in 376, is Bishop of Alexandria in 412 and dies on 27 June 444. He is also, since the proclamation of Pope Leo XIII in 1882, Father and Doctor of the Catholic Church.

Patriarch of Alexandria, nephew and successor of Theophilus, Cyril endeavoured to eradicate paganism, Judaism and what he considered to be heresies: he wrote against the Arians and Antiochians, and had the synagogues and churches of the Novatians closed. He thus annihilated the Jewish community and in the same way attacked other Christian communities labelled as heretics. These measures set him against Oreste, Prefect of Egypt, who was also a Christian.

Cyril promoted the formula "One is the incarnate nature of God the Word", by which he opposed the duality of natures defended by the Antiochians. This formula was widely used during the crisis and the monophysite schism. His Christological positions are summed up in the Symbol of Union which he signed in 433, two years after the clashes of the Council of Ephesus, with John, the patriarch of Antioch.

Cyril, Bishop of Alexandria and Doctor of the Church, actively participated in the Council of Ephesus (431), which gave Mary the title of "Mother of God". He was a prolific exegete as well as an ardent defender of faith in Christ. In an audience on October 3, 2007, Benedict XVI paid tribute to him for his important contribution to Marian worship.