Saint Cyril was a 9th-century Christian missionary known for his work in spreading Christianity among the Slavic peoples. Along with his brother, Saint Methodius, he developed the Glagolitic alphabet, which was the first alphabet used to write the Old Church Slavonic language. This innovation helped to translate the Bible and other religious texts, making them accessible to the Slavic population. Cyril's contributions to language and culture earned him the title of a patron saint of Slavic peoples. His feast day is celebrated on February 14, honoring his legacy in promoting literacy and faith. Today, he is remembered for his significant role in shaping Slavic identity and culture.