The traditional lands of the Czech-speaking people are Bohemia, Moravia and parts of Silesia, and it is these provinces that make up the modern Czech Republic (though only part of historical Silesia). The origin of the name ‘Bohemia’ itself, however, has nothing to do with Slavonic culture at all, but rather the Boii, a Celtic tribe that inhabited that region until around the first century AD. The Boii were driven westward by Germanic tribes from the area around modern-day Bavaria, who were then, in turn, driven back westward by Slavic tribes from the east. These Slavic tribes contributed to the massive Great Moravian Empire, which, during the ninth to tenth centuries, extended from their present borders as far as the Black Sea. The most significant historical importance of this new empire is that its success drew attention from both east and west and resulted in the Christianisation of its Slavic-speaking subjects.

In around the year 860, Louis the Germanic King of the East Franks tried to get involved with the conversion of the Bulgarians with the hope of having leverage on the other side of the vexatious Moravians. His action had the important, though unintended, result of pushing the Moravians into the arms of Constantinople. In 863, at the request of Prince Rastislav of Moravia, Patriarch Photius sent two brothers, Cyril and Methodius, to preach Christianity in the Slavic tongue to the Moravians.