Born to a wealthy middle-class family in Simbirsk, Lenin embraced revolutionary socialist politics following his brother's 1887 execution. Expelled from Kazan Imperial University for participating in protests against the Russian Empire's Tsarist government, he devoted the following years to a law degree. He moved to Saint Petersburg in 1893 and became a senior Marxist activist. In 1897, he was arrested for sedition and exiled to Shushenskoye for three years, where he married Nadezhda Krupskaya. After his exile, he moved to Western Europe, where he became a prominent theorist in the Marxist Russian Social Democratic Labour Party (RSDLP). In 1903, he took a key role in a RSDLP ideological split, leading the Bolshevik faction against Julius Martov's Mensheviks. Encouraging insurrection during Russia's failed Revolution of 1905, he later campaigned for the First World War to be transformed into a Europe-wide proletarian revolution, which as a Marxist he believed would cause the overthrow of capitalism and its replacement with socialism. After the 1917 February Revolution ousted the Tsar and established a Provisional Government, he returned to Russia to play a leading role in the October Revolution, in which the Bolsheviks overthrew the new regime.
Lenin's Bolshevik government initially shared power with the Left Socialist Revolutionaries, elected soviets, and a multi-party Constituent Assembly, although by 1918 it had centralised power in the new Communist Party. Lenin's administration redistributed land among the peasantry and nationalised banks and large-scale industry. It withdrew from the First World War by signing a treaty with the Central Powers and promoted world revolution through the Communist International. Opponents were suppressed in the Red Terror, a violent campaign administered by the state security services; tens of thousands were killed or interned in concentration camps. His administration defeated right and left-wing anti-Bolshevik armies in the Russian Civil War from 1917 to 1922 and oversaw the Polish–Soviet War of 1919–1921. Responding to wartime devastation, famine, and popular uprisings, in 1921 Lenin encouraged economic growth through the market-oriented New Economic Policy. Several non-Russian nations secured independence after 1917, but three re-united with Russia through the formation of the Soviet Union in 1922. In increasingly poor health, Lenin expressed opposition to the growing power of his successor, Joseph Stalin, before dying at his dacha in Gorki.
Widely considered one of the most significant and influential figures of the 20th century, Lenin was the posthumous subject of a pervasive personality cult within the Soviet Union until its dissolution in 1991. He became an ideological figurehead behind Marxism–Leninism and thus a prominent influence over the international communist movement. A controversial and highly divisive individual, Lenin is viewed by supporters as a champion of socialism and the working class, while critics on both the left and right emphasize his role as founder and leader of an authoritarian regime responsible for political repression and mass killings.
Lenin's father, Ilya Nikolayevich Ulyanov, was from a family of serfs; his ethnic origins remain unclear, with suggestions being made that he was Russian, Chuvash, Mordvin, or Kalmyk. Despite this lower-class background he had risen to middle-class status, studying physics and mathematics at Kazan Imperial University before teaching at the Penza Institute for the Nobility. Ilya married Maria Alexandrovna Blank in mid-1863. Well educated and from a relatively prosperous background, she was the daughter of a German–Swedish mother and a Russian Jewish father who had converted to Christianity and worked as a physician. It is likely that Lenin was unaware of his mother's half-Jewish ancestry, which was only discovered by his sister Anna after his death. Soon after their wedding, Ilya obtained a job in Nizhny Novgorod, rising to become Director of Primary Schools in the Simbirsk district six years later. Five years after that, he was promoted to Director of Public Schools for the province, overseeing the foundation of over 450 schools as a part of the government's plans for modernisation. His dedication to education earned him the Order of St. Vladimir, which bestowed on him the status of hereditary nobleman.
Lenin was born in Simbirsk on 22 April 1870 and baptised several days later; as a child, he gained the nickname of "Volodya," a dimunitive of Vladimir. He was one of eight children, having two older siblings, Anna (born 1864) and Alexander (born 1868). They were followed by three more children, Olga (born 1871), Dmitry (born 1874), and Maria (born 1878). Two later siblings died in infancy. Ilya was a devout member of the Russian Orthodox Church and baptised his children into it, although Maria—a Lutheran by upbringing—was largely indifferent to Christianity, a view that influenced her children.