Bogomils, members of a religious sect that arose in the 10th century in the Balkans. The chief centre was in Bulgaria and the cult spread among other Slavic peoples. The movement resulted from a blending of Eastern dualism and an evangelical attempt to reform the Bulgarian Orthodox Church. The Bogomils, whose fundamental doctrines are attributed to a priest called Bogomil, held that the first-born son of God was Satanael. Satanael rebelled and created, in opposition to the original spiritual universe, a world of matter and human beings. The Supreme Father gave these human beings a life spirit. This life spirit, however, was kept in slavery by Satanael until a second son of God, the Logos, or Christ, came down from heaven and, assuming a phantom body, broke the power of the evil spirit, who was henceforth called only Satan, the divine name, El, being dropped. The Bogomils practised a severe asceticism, despised images, and rejected the sacraments. They accepted the whole of the New Testament, but of the Old Testament only the Psalms and Prophets, which they interpreted allegorically. The morals and ideals of the Bogomils seem to have been much above the average of their time.

In 1118 the Byzantine Emperor Alexius I Comnenus executed the leader of the sect for heresy. At the time of the Muslim conquest of Bosnia in the 15th century, the majority of the Christians who embraced Islam, the religion of the conquerors, were Bogomils. Before the Bogomils were suppressed they influenced the development of the Albigensian and Cathari groups of France and Italy in the 12th and 13th centuries.