The Socialist-Revolutionary Party (SRs, or Essaires; Партия социалистов-революционеров (ПСР), эсеры in Russian) were a Russian political party active in the early 20th century.
Their programme was in the democratic socialist mold and garnered much support amongst Russia's rural peasantry who in particular supported their programme of land-socialisation as opposed to the Bolshevik programme of land-nationalisation. Their policy platform could be broadly described as left-wing, although more moderate than that of the Bolsheviks. They grew directly out of the populist movement. With the economic spurt in Russia of the 1890s they attempted to broaden their basis of appeal in order to attract the rapidly growing urban workforce to their traditionally peasant orientated programme. The intention was to widen the concept of the 'people' so that it encompassed all those elements in society that had reason for wishing to see the destruction of the Tsarist system.
The Russian Revolution of February, 1917 brought the SRs a more prolific political role, with one of their members Alexander Fedorovich Kerensky joining the liberal government, eventually becoming the head of government.
In 1917 the SRs split between those who supported the Provisional Government, established after the February Revolution, and those who supported the Bolsheviks who favoured a communist revolution. Those who supported revolution became known as Left Socialist-Revolutionaries (Left Esers) and in effect split from the main party, which has become known as Right Esers.
The SRs faded after the October Revolution brought the Bolsehviks to power although in the election to the Constituent Assembly they proved to be the most popular party across the country, gaining some 40% of the popular vote as opposed to the Bolsheviks 25%. However, the Bolsheviks disbanded the Assembly and thereafter the SRs become of less political significance, although some left-SRs did become part of the government of the Soviet Union, although they resigned their positions after the Treaty of Brest-Litovsk was signed. A few left-SRs joined the Communist Party.
Many SRs fought for the Greens in the Russian Civil War alongside Mensheviks and other banned moderate socialist elements. An SR, Fanya Kaplan tried to assassinate Lenin in response to their proscription. The largest Tambov Rebellion against Bolsheviks was led by an eser Alexander Antonov.