Saints Cyril and Methodius were Byzantine Greek brothers born in Thessaloniki in the 9th century, who became missionaries of Christianity among the Slavic peoples of Great Moravia and Pannonia.

They became missionaries, teachers and patrons of the Slavic peoples. The day commemorates the creation of the Slavic Glagolitic and Cyrillic alphabets by the brothers Saints Cyril and Methodius.

In the Czech Republic it is celebrated on July 5 as a national holiday.

In the Republic of Macedonia, it is celebrated on May 24 and is known as the 'Saints Cyril and Methodius, Slavonic Enlighteners Day'. It is a public holiday.

In Slovakia, a public holiday, celebrated on July 5 as 'St. Cyril and Metod Day'.