Boris Ivanovich Nicolaevsky (Russian: Борис Иванович Николаевский) (1887-1966) was a revolutionary Russian Marxist activist, archivist, and historian. Nicolaevsky is best remembered as one of the leading Menshevik public intellectuals of the 20th Century.
Boris Nicolaevsky was born October 20, 1887 N.S. in Belebey, Bashkiria, then part of the Russian empire.
Nicolaevsky became a member of the Menshevik wing of the Russian Social Democratic Labor Party when he was still a youth. He was subsequently arrested eight times and sent into Siberian exile three times by the Tsarist government.
Following the Russian Revolution of 1917, Nicolaevsky became the head of the Marx-Engels Institute in Moscow.
As an active Menshevik, Nicolaevsky was arrested by the Soviet secret police in 1921 and deported from Soviet Russia in 1922. He subsequently moved to Berlin, where he was associated with the Marx-Engels Institute there, before becoming the director of the International Institute of Social History in Amsterdam, repository of the archives of the Socialist International.