The Red Army Faction or Red Army Fraction (RAF; German: Rote Armee Fraktion), in its early stages commonly known as Baader-Meinhof Group (or Baader-Meinhof Gang), was one of post–World War II Germany's most prominent left-wing militant groups. The RAF was founded in 1970 by Andreas Baader, Gudrun Ensslin, Horst Mahler, and Ulrike Meinhof. The RAF described itself as a communist and anti-imperialist "urban guerrilla" group engaged in armed resistance against what they deemed to be a fascist state. As such, members of the RAF generally used the Marxist-Leninist term "Faction" when they wrote in English.

The Red Army Faction existed from 1970 to 1998, committing numerous operations, especially in late 1977, which led to a national crisis that became known as "German Autumn". It was held responsible for thirty-four deaths, including many secondary targets, such as chauffeurs and bodyguards, and many injuries in its almost thirty years of activity. Although better-known, the RAF conducted fewer attacks than the Revolutionary Cells (RZ), which is held responsible for 296 bomb attacks, arson and other attacks between 1973 and 1995.

The Workers' and Peasants' Red Army (Russian: Рабоче-Крестьянская Красная Армия; РККА or Rabočě-Krěst'janskaja Krasnaja Armija; RKKA) started out as the Soviet Union's revolutionary communist combat groups during the Russian Civil War of 1918–1922. It grew into the national army of the Soviet Union. By the 1930s the Red Army was among the largest armies in history.

The "Red Army" refers to the traditional colour of the Communist movement. On 25 February 1946 (when Soviet national symbols replaced revolutionary symbols), the Red Army was renamed the Soviet Army (Советская Армия, Sovetskaya Armiya).

The Red Army is widely credited with being the decisive force in the Allied victory in the European Theatre of World War II, having engaged and defeated about 80% of the German armed forces, the Wehrmacht and much of the Waffen SS on the Eastern Front.

In September 1917 V. I. Lenin wrote "There is only one way to prevent the restoration of the police, and that is to create a people's militia and to fuse it with the army (the standing army to be replaced by the arming of the entire people)."