For the first time in domestic and foreign historiography, the book explores the history of the unique research institution of the Communist Party of the USSR - the Institute of Marxism-Leninism (IML) under the Central Committee of the CPSU for all 70 years of its activity, from 1921 to 1991. Through the prism of the history of IML, the role of the ideology of Marxism-Leninism in the life of Soviet society can be traced - from the rallying, mobilizing factor to its transformation into an orthodox, dogmatic doctrine, the observance of which led to the collapse of the USSR.