Melvin Floyd Sembler (born May 10, 1930) is former United States Ambassador to Italy (2001–2005), and former Ambassador to Australia and Nauru (1989–1993). He has also served as Chairman of the Board of the Sembler Company, which develops and manages shopping centers, and co-founder of Straight, Inc., a controversial drug-treatment center. Sembler is the chairman of the Scooter Libby Legal Defense Trust, and was a co-chair of the Florida Finance Committee for Mitt Romney.