Karl Johann Franz Formes (b. Mülheim am Rhein, 7 August 1815; d. San Francisco, 15 December 1889), also called Charles John Formes, was a German bass opera and oratorio singer who had a long international career especially in Germany, London and New York. At one time extremely famous and in the forefront of his profession, several roles were composed for his voice, most notably that of Plunkett in Flotow's opera Martha.