Murder, Inc. was an organized crime group active from 1929 to 1941 that acted as the enforcement arm of the National Crime Syndicate – a closely connected criminal organization that included the Italian-American Mafia, the Jewish Mob, and other criminal organizations in New York City and elsewhere. Murder, Inc. was composed of Jewish and Italian-American gangsters, and members were mainly recruited from poor and working-class Jewish and Italian neighborhoods in Manhattan and Brooklyn. It was initially headed by Louis "Lepke" Buchalter and later by Albert "Mad Hatter" Anastasia.

Jewish-American organized crime initially emerged within the American Jewish community during the late 19th and early 20th centuries. In media and popular culture, it has variously been referred to as the Jewish Mob, the Jewish Mafia, the Kosher Mob, the Kosher Mafia, the Yiddish Connection, and Kosher Nostra or Undzer Shtik. The last two of these terms are direct references to the Italian cosa nostra; the former is a play on the word for kosher, referring to Jewish dietary laws, while the latter is a calque of the Italian phrase 'cosa nostra' into Yiddish, which was at the time the predominant language of the Jewish diaspora in the United States.