Florence Mendheim (January 13, 1899 – August 1984)[1] was a New York Public Library branch librarian notable for her undercover surveillance of American Nazi groups in the pre-World War II 1930s.

Her personal papers, including documentation of her spy activities, are housed in the archives of the Leo Baeck Institute in New York.

Correspondence from library administrators and supervisors[3] indicate Ms. Mendheim had chronic health problems that led to her early retirement in the late 1940s, although little is known of her personal life.

Under the assumed identity of Gertrude Mueller, Mendheim attended pro-Nazi meetings and rallies, and eventually accumulated a sizable collection of anti-Semitic propaganda produced locally, nationally, and abroad.

According to archival documents,[7] Mendheim's purchases of Nazi propaganda and literature were reimbursed by Rabbi Jacob Xenab Cohen of the American Jewish Congress, to whom she submitted regular narrative reports of her activities.