Saints Cyril and Methodius were Byzantine Greek brothers born in Thessaloniki in the 9th century who became Christian missionaries among the Slavic peoples of the Great Moravia and Pannonia. Through their work they influenced the cultural development of all Slavs, for which they received the title "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 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.
Lord of all,
who gave to your servants Cyril and Methodius
the gift of tongues to proclaim the gospel to the Slavs:
make your whole Church one as you are one
that all Christians may honour one another,
and east and west acknowledge
one Lord, one faith, one baptism,
and you, the God and Father of all;
through Jesus Christ our Lord.