Karl Herxheimer (June 26, 1861 - December 6, 1942) was a German-Jewish dermatologist who was a native of Wiesbaden.
In 1885 he received his doctorate at Würzburg, and later worked with his brother, Salomon Herxheimer (1841-1899) in Frankfurt-am-Main. In 1894 he became director of the dermatology clinic in Frankfurt, and with Paul Ehrlich (1854-1915), was instrumental in founding the University of Frankfurt. In 1914 he became professor for skin and venereal diseases at the new university. In late 1942, at the age of 81, Karl Herxheimer was taken to the Theresienstadt concentration camp where he died.