Cyril and Methodius
Cyril (Greek: Κύριλλος, romanized: Kýrillos; born Constantine [Greek: Κωνσταντίνος, romanized: Konstantínos]; 826–869) and Methodius (Μεθόδιος, Methódios; born Michael [Greek: Μιχαήλ, romanized: Michaíl]; 815–885) were brothers, Byzantine Christian theologians and missionaries. For their work evangelizing the Early Slavs, they are known as the "Apostles to the Slavs".