Cyril, St (d. 444). Patriarch of Alexandria from 412, and church father. His career after c.430 was dominated by the controversy over church authority (he drove out schismatic followers of Novatian), christology, and specifically by his opposition to Nestorius. The Neoplatonist philosopher, Hypatia, was murdered by the mob, possibly at Cyril's instigation. The episode evoked a novel by Charles Kingsley. In the E. he is ‘the Seal of the Fathers’, in the W. a doctor of the Church (since 1882).

Cyril, St (826–69), Greek missionary. He and his brother, St Methodius, were sent to Moravia where they taught in the vernacular, which they adopted also for the liturgy, and circulated a Slavic version of the scriptures. His feast day (in the Eastern Church) is 11 May; (in the Western Church) is 14 February.

The invention of the Cyrillic alphabet, used by many Slavic peoples, chiefly those with a historical allegiance to the Orthodox Church, is ascribed to him. Ultimately derived from Greek uncials, it is now used for Russian, Bulgarian, Serbian, Ukrainian, and some other Slavic languages.

Cyril, Saint (826–69) Greek Christian missionary. With his brother, Methodius, he is one of the two so-called “Apostles to the Slavs” who were sent to convert the Khazars and Moravians to Christianity. Cyril is said to have invented the Cyrillic alphabet. His feast day is February 14 (West); May 11 (East).