Bogomilism was a Christian neo-Gnostic, dualist sect founded in the First Bulgarian Empire by the priest Bogomil during the reign of Tsar Peter I in the 10th century. It most probably arose in the region of Kutmichevitsa, today part of the region of Macedonia.

Dualism in cosmology or dualistic cosmology is the moral or spiritual belief that two fundamental concepts exist, which often oppose each other. It is an umbrella term that covers a diversity of views from various religions, including both traditional religions and scriptural religions.