Józef Światło, born Izaak Fleischfarb (1 January 1915 – 2 September 1994), was a high-ranking official in the Ministry of Public Security of Poland (MBP) who served as deputy director of the 10th Department run by Anatol Fejgin. Known for supervising the torture of prisoners, he was nicknamed "the Butcher" by MBP prisoners. After the 1953 death of Joseph Stalin and arrest of Lavrentiy Beria, Światło traveled to East Germany on official business. While on the Berlin subway with Fejgin, passing through West Berlin, on 5 December 1953, he "slipped away" and defected to the West. Afterward he worked for the American Central Intelligence Agency and Radio Free Europe. Światło's written and broadcast denunciations shook the Polish United Workers' Party. This ultimately contributed to post-Stalinist reforms of the Polish security apparatus and to Poland's political liberalisation in the socialist Polish October revolution.