Fyodor Ilyich Dan (Russian: Фёдор Ильич Дан), often known in English as Fedor Dan, (19 October 1871 – 22 January 1947) was one of the founding leaders of Menshevism. His wife was fellow Menshevik Lydia Dan.
Fyodor Dan was born to a Jewish family in St. Petersburg. His original surname was Gurvitch.
Dan was a lifelong socialist reformist activist.
While still a young man he joined the Union of Struggle for the Emancipation of the Working Class. He was arrested in 1896 and exiled in Oryol for three years.
On his return he joined the Russian Social Democratic Labour Party and went to London for their Second Congress in 1903. Dan aligned himself with Julius Martov who wanted to have a larger party of activists, rather than Vladimir Lenin's conception of a smaller party of professional revolutionaries. Dan helped Martov form the Mensheviks, returning to Russia in 1912.
Living in St Petersburg, he edited Menshevik publications until facing exile to Minusinsk following the outbreak of World War I. He was released in 1915 when he agreed to serve in the Army as a surgeon. He returned to St Petersburg following the February Revolution and argued for Menshevik involvement in the Provisional Government. He also argued for continuing the war against Germany and Austria.
In 1917 he was the leading Menshevik on the praesidium of the Petrograd Soviet. He opposed the October Revolution and he was a member of the small oppositional group in the Russian Constituent Assembly. However this was banned in 1918. Dan continued to denounce the curtailment of political freedoms, linking Bolshevism with Bakuninism.