Jean-Baptiste Frédéric Isidor, Baron Thielemans (born 29 April 1922, Brussels, Belgium), known as Toots Thielemans, is a Belgian jazz musician well known for his guitar and harmonica playing as well as his whistling. Thielemans is credited as one of the greatest harmonica players of the 20th century.
He has worked as a bandleader (scoring an international hit in the 1960s with his song "Bluesette"), as a sideman (notably on many projects with composer/arranger Quincy Jones), and has appeared on dozens of film soundtracks. In 2009 he became NEA Jazz Master, the highest honour for a jazz musician in the United States.
He may be best-known to some of the American public as the performer whistling the melody in commercials for Old Spice cologne.