Pyotr Nikitich Tkachev (Russian: ???? ??????? ??????) (29 June 1844 – 4 January 1886) was a Russian writer, critic and revolutionary theorist, who it is claimed formulated many of the revolutionary principles that would later be further developed and put into action by Vladimir Lenin.
Although Tkachev has sometimes been described as "the First Bolshevik", he did not figure prominently in the mythology of the Soviet Union.