Lehi, often known pejoratively as the Stern Gang, was a Zionist paramilitary militant organization founded by Avraham ("Yair") Stern in Mandatory Palestine. Its avowed aim was to evict the British authorities from Palestine by use of violence, allowing unrestricted immigration of Jews and the formation of a Jewish state. It was initially called the National Military Organization in Israel, upon being founded in August 1940, but was renamed Lehi one month later. The group referred to its members as terrorists and admitted to having carried out terrorist attacks.

Avraham Stern, alias Yair, was one of the leaders of the Jewish paramilitary organization Irgun. In September 1940, he founded a breakaway militant Zionist group named Lehi, called the "Stern Gang" by the British authorities and by the mainstream in the Yishuv Jewish establishment. The group referred to its members as terrorists and admitted to having carried out terrorist attacks.