Sergei Mironovich Kirov (Russian: Серге́й Миро́нович Ки́ров) born Kostrikov (Ко́стриков; 27 March [O.S. 15 March] 1886 – 1 December 1934) was a prominent early Bolshevik leader in the Soviet Union. Kirov rose through the Communist Party ranks to become head of the party organization in Leningrad.