The Marx–Engels–Lenin Institute (Russian: Институт Маркса — Энгельса — Ленина, Institut Marksa – Engelsa – Lenina), established in Moscow in 1919 as the Marx–Engels Institute (Russian: Институт К. Маркса и Ф. Энгельса, Institut K. Marksa i F. Engelsa), was a Soviet library and archive attached to the Communist Academy. The institute was later attached to the governing Central Committee of the Communist Party of the Soviet Union and served as a research center and publishing house for officially published works of Marxist thought. From 1956 to 1991, the institute was named the Institute of Marxism–Leninism (Russian: Институт марксизма-ленинизма, Institut Marksizma-Leninizma; IML, Russian: ИМЛ).
The Marx–Engels Institute gathered unpublished manuscripts by Karl Marx, Friedrich Engels, Vladimir Lenin and other leading Marxist theoreticians as well as collecting books, pamphlets and periodicals related to the socialist and organized labor movements. By 1930, the facility's holdings included more than 400,000 books and journals and more than 55,000 original and photocopy documents by Marx and Engels alone, making it one of the largest holdings of socialist-related material in the world.