The article concerns the evolution process of Pan-Mongolism as a phenomenon from “cultural Pan-Mongolism” to state ideology as a result of the Xinhai Revolution of 1911–1913 and Kyakhta tri-partite agreement. The role of the Russian Empire and efforts of Russian diplomatic service are specifically highlighted. A significant issue of the research is the role of Bogdo-gegen in the history of contemporary Mongolia. Bodgo-gegen became a leader of the Mongolian theocratic state and an ideologist of Pan-Mongolism.