Toots Thielemans (born Jean-Baptiste Frédéric Isidor, Baron Thielemans, 29 April 1922, Brussels, Belgium) is a Belgian jazz musician 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") and 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.