The war crimes and crimes against humanity which were perpetrated by the Soviet Union and its armed forces from 1919 to 1991 include acts which were committed by the Red Army (later called the Soviet Army) as well as acts which were committed by the country's secret police, NKVD, including its Internal Troops. In many cases, these acts were committed upon the orders of the Soviet leaders Vladimir Lenin and Joseph Stalin in pursuance of the early Soviet government's policy of Red Terror. In other instances they were committed without orders by Soviet troops against prisoners of war or civilians of countries that had been in armed conflict with the USSR, or they were committed during partisan warfare.
A significant number of these incidents occurred in Northern, Central, and Eastern Europe recently before, and during, the aftermath of World War II, involving summary executions and the mass murder of prisoners of war, such as in the Katyn massacre and mass rape by troops of the Red Army in territories they occupied.
In the 1990s and 2000s, war crimes trials held in the Baltic states led to the prosecution of some Russians, mostly in absentia, for crimes against humanity committed during or shortly after World War II, including killings or deportations of civilians. Today, the Russian government engages in historical negationism. Russian media refers to the Soviet crimes against humanity and war crimes as a "Western myth". In Russian history textbooks, the atrocities are either altered to portray the Soviets positively or omitted entirely. In 2017, Russian President Vladimir Putin, himself a war crime fugitive since 2023, while acknowledging the "horrors of Stalinism", criticized the "excessive demonization of Stalin" by "Russia's enemies".
The Soviet Union did not recognize Imperial Russia's signing of the Hague Conventions of 1899 and 1907 as binding, and as a result, it refused to recognize them until 1955. This created a situation in which war crimes by the Soviet armed forces could eventually be rationalized, and also gave Nazi Germany a legal fig leaf for the atrocities it committed against Soviet prisoners of war.