
Saints Cyril and Methodius, who created the Cyrillic Alphabet
("Cyril", "Cyrillic", get it, DU onlurkers?), most likely were Greek, or possibly non-Russian Slavs. They were born in Thessaloniki, which is part of modern Greece, in the Byzantine Empire.

They created that alphabet in their missionary work in Great Moravia, which included parts of the Czech Republic, Slovakia, Hungary, Austria, Germany, Poland, Romania, Serbia, and Ukraine
(a further clue for DU onlurkers, notice which modern country was part of that territory and which is not?).