The Vinnytsia massacre was a mass execution of between 9,000 and 11,000 people in the Ukrainian town of Vinnytsia by the Soviet secret police NKVD during the Great Purge or Yezhovshchina in 1937–1938. Mass graves in Vinnytsia were discovered during Nazi Germany's occupation of Ukraine in 1943. The investigation of the site first conducted by the international Katyn Commission coincided with the discovery of a similar mass murder site of Polish prisoners of war in Katyn. Nazi Germany utilized this evidence of Communist terror to discredit the Soviet Union internationally. It became one of the better known sites of politically motivated NKVD massacres among many in Ukraine.