Karl Fabel (October 20, 1905 Hamburg – 3 March 1975, Egenhofen) was a German chess composer.
Fabel received a doctorate in chemistry and worked as a mathematician and civil judge at the federal office of brands and patents in Munich, of which he was also president.
He is considered one of the most ingenious chess composers and one of the fathers of retrograde analysis, frequently collaborating with Luigi Cerianiin this area. He composed around 1250 problems of all varieties. He studied chess problems of a mathematical nature such as the Eight queens puzzle, the Knight's tour and Shannon's number. He was a director of Die Schwalbe.