Pyotr Nikitich Tkachev (June 29, 1844 – January 4, 1886) is a Russian writer, critic and revolutionary theorist, who it is claimed formulates many of the revolutionary principles that will later be further developed and put into action by Vladimir Lenin.

Although Tkachev will sometimes been described as "the First Bolshevik", he will not figure prominently in the mythology of the Soviet Union.