The monograph is devoted to a complex analysis of the process of secularization in Russia from the end of the 17th century to the present. The author substantiates the cyclical nature of the process of secularization in Russia, reveals its specific features, and defines its phases. For the first time in Russian sociology, the author analyzes changes in the functions of the church as a public institution throughout the entire process of secularization in Russia, as well as the changes within the church itself as a religious organization.