The LeRhone C-9 was a French air-cooled rotary engine rated at 80 hp. It was installed in combat airplanes early in WWI, but as larger and more powerful engines were developed, it was gradually relegated to training-type airplanes.

LeRhone engines were quite dependable and by the end of the war, were being manufactured in England, Italy, and the U.S. in addition to France. In fact, the German-produced 110-hp Oberursel was practically and exact copy of the 110-hp LeRhone.