The author studies the role of Christianity in two forms of 9th century political ethics in the history of Great Moravia, represented by the Great Moravian rulers Rastislav and Svatopluk. Rastislav’s conception predominantly uses the pre-Erasmian model of political ethics based on the pursuit of welfare for the country and its inhabitants by achieving the clerical-political independence of Great Moravia from the Frankish kingdom and, moreover, by utilising Christianity for the advancement of culture, education, literature, law and legality, as well as by spreading Christian ethics and morality in the form of the Christian code of ethics expressed in ethicallegal documents. Svatopluk’s political conception was a prototype of Machiavellian political ethics, according to which one is, in the interest of the country and its power and fame, allowed to be a lion and/or a fox. Svatopluk abused Christianity in the name of achieving his power-oriented goals. Great Moravia outlived Rastislav; it did not, however, outlive Svatopluk, as, shortly after his death, it broke up and ceased to exist. The author came to the conclusion that Rastislav’s conception was more viable, as its cultural heritage lives on in the form of works by Constantine and Methodius.