Fyodor Dan (born Fyodor Ilyich Gurvich; 1871–1947) was a Russian revolutionary, physician, and a prominent leader of the Menshevik faction of the Russian Social Democratic Labour Party (RSDLP). He was a significant figure in the Russian socialist movement during the early 20th century and a key political opponent of Vladimir Lenin.
Born in Saint Petersburg, Dan became involved in revolutionary activities in the 1890s and was a founding member of the Union of Struggle for the Emancipation of the Working Class. Following the 1903 split of the RSDLP, he aligned with the Mensheviks, advocating for a democratic, mass-based labor party rather than the centralized vanguard model proposed by the Bolsheviks. He was a close associate and brother-in-law of Julius Martov, the primary leader of the Mensheviks.
During the Russian Revolution of 1905, Dan was active in organizing labor strikes and editing socialist periodicals. Following the February Revolution of 1917, he emerged as a leading member of the Petrograd Soviet and served on the All-Russian Central Executive Committee of Soviets. He supported the Russian Provisional Government and championed the policy of "Revolutionary Defencism," which argued for continuing Russia's participation in World War I to defend the revolution against foreign autocracy.
After the October Revolution and the Bolshevik seizure of power, Dan remained in Russia as a leader of the legal Menshevik opposition. However, as the Bolsheviks consolidated power and suppressed dissenting socialist parties, Dan was arrested in 1921. In 1922, he was among the group of intellectuals and political dissidents permanently exiled from the Soviet Union.
In exile, Dan lived in Berlin, Paris, and eventually New York City. He continued his political work as an editor of the Menshevik journal Sotsialisticheskiy Vestnik (Socialist Courier). In his later years, he authored The Origins of Bolshevism (published posthumously), a historical and sociological analysis of the Russian revolutionary movement. He died in New York in 1947.