Leon Lawrence Lewis (September 5, 1888 – May 21, 1954) was an American attorney, the first national secretary of the Anti-Defamation League, the national director of B'nai B'rith, the founder and first executive director of the Los Angeles Jewish Community Relations Committee, and a key figure in the spy operations that infiltrated American Nazi organizations in the 1930s and early 1940s. The Nazis referred to Lewis as "the most dangerous Jew in Los Angeles."