The article is devoted to the study of the genesis of religious ideas of the Ket and Selkup ethnocultural groups in a historical and cultural context. On the basis of the ethnographic and linguistic material, the article describes the current state of religion and culture of the Kets and Selkups, provides an analytical review of classical and modern studies reflecting the dynamics of the development of religious ideology in the territories inhabited by these ethnic groups. Despite the official Christianization, both the Kets and the Selkups have retained their traditional cosmological and ideological views for many years. Their religious ideology is characterized by coexistence of beliefs and rites of different origins and specificities that reflect natural, everyday, economic and social conditions of ethnic communities. The key manifestations of religious ideology include the idea of the three-part structure of the universe, animistic and ancient totemic beliefs, developed trade ideology, shamanism, burial rites and folklore.