The October Revolution (Russian: Октя́брьская револю́ция, tr. Oktyabr'skaya revolyutsiya; IPA: [ɐkˈtʲæbrʲskəjə rʲɪvɐˈlʲʉtsɨjə]), also known as the Great October Socialist Revolution (Russian: Вели́кая Октя́брьская социалисти́ческая револю́ция, tr. Velikaya Oktyabr'skaya sotsialisticheskaya revolyutsiya), Red October, the October Uprising or the Bolshevik Revolution, was a political revolution, mass insurrection and a part of the Russian Revolution of 1917. It took place with an armed insurrection in Petrograd traditionally dated to 25 October 1917 Old Style Julian Calendar (O.S.), which corresponds with 7 November 1917 New Style (N.S.).Gregorian Calendar.

It followed and capitalized on the February Revolution of the same year. The October Revolution in Petrograd overthrew the Russian Provisional Government and gave the power to the local soviets dominated by Bolsheviks. As the revolution was not universally recognized outside of Petrograd there followed the struggles of the Russian Civil War (1917–1923) and the creation of the Soviet Union in 1922.