Szmalcownik

thumb|200px|Polish underground Biuletyn Informacyjny (Information Bulletin), 2 September 1943, announcing death sentences carried out on collaborators, including a szmalcownik named Jan Grabiec thumb|Announcement by the governor of the Warsaw District, [[Ludwig Fischer, of 13 May 1943, encouraging the inhabitants of Warsaw to hand over communist agents and Jews to the German authorities]] thumb|200px|Directorate of Underground Resistance poster, September 1943, announcing death sentences carried out on collaborators, including Bogusław Jan Pilnik, sentenced for 'blackmailing, and delivering to German authorities, hiding Polish citizens of Jewish ethnicity" thumb|Żegota communiqué published in September 1943 warning that denunciation of Jews to the Nazis was a capital offence

Szmalcownik (); in English, also sometimes spelled shmaltsovnik) is a pejorative Polish slang expression that originated during the Holocaust in Poland in World War II and refers to a person who blackmailed Jews who were in hiding, or who blackmailed Poles who aided Jews, during the German occupation. By stripping Jews of their financial resources, blackmailers added substantially to the danger that Jews and their rescuers faced and increased their chances of being caught and killed.