Cyril (born Constantine, 826–869) and Methodius (815–885) were two brothers and Byzantine Christian theologians and missionaries. For their work evangelizing the Slavs, they are known as the “Apostles to the Slavs”.

They are credited with devising the Glagolitic alphabet, the first alphabet used to transcribe Old Church Slavonic. After their deaths, their pupils continued their missionary work among other Slavs. Both brothers are venerated in the Eastern Orthodox Church as saints with the title of “equal-to-apostles“. In 1880, Pope Leo XIII introduced their feast into the calendar of the Roman Catholic Church. In 1980, Pope John Paul II declared them co-patron saints of Europe, together with Benedict of Nursia.