The monograph is devoted to the study of various aspects of the history of single-faith. The process of formation and development of single-faith in the Russian Empire is being reconstructed. On rich archival material, regional variations of single-faith are highlighted and described. Relations between co-religionists and Old Believers, hierarchs of the official church and the state are considered. Attention is paid to the intellectual history of co-faith, as well as the controversy between co-religionists and Old Believers. For historians and anyone interested in the history of single-faith and Old Believers in Russia.