Cyril of Alexandria was a 5th-century theologian and the Patriarch of Alexandria, serving from 412 until his death in 444. Born around 376 in Egypt, he was educated under the guidance of his uncle, Theophilus. He became a central figure in the Christological debates of his era, most notably presiding over the Council of Ephesus in 431. During this council, he helped establish the doctrine of the hypostatic union and championed the use of the title Theotokos for the Virgin Mary. He is recognized as a saint in several Christian traditions.