Jankiel (Yankel, Yaakov, or Jacob) Wiernik (Hebrew: יעקב ויירניק‎) (1889–1972) was a Polish-Jewish Holocaust survivor who was an influential figure in the Treblinka extermination camp resistance. He had been forced to work as a Sonderkommando slave worker there, where an estimated 700,000-900,000 people, mostly Jews were murdered. After his escape during the uprising of 2 August 1943, Wiernik reached Warsaw and joined the resistance. He also wrote a clandestine account of the camp's operation, A Year in Treblinka, which was copied and translated for printing in London and the US in English and Yiddish.