The Conrad C.III was a six-cylinder, water-cooled inline aircraft engine designed by Robert Conrad. It was used on some German training aircraft during World War I. The engine was mainly produced under license by the German Nationale Automobil Gesellschaft.
After having designed two aircraft engines for the German Kaiserpreis aero-engine competition of 1912–1913, Robert Conrad prepared an 180 hp (134 kW) six-cylinder aircraft engine for the second Kaiserpreis competition anticipated to take place in 1914–1915. Further improvements on the engine design were done in 1915 by Robert Conrad while he was working for the Deutsche Motorenbau-Gesellschaft. His work resulted in a six-cylinder water-cooled engine with increased bore which was capable of delivering 185 hp (138 kW) at 1400 rpm. After a successful type test in February 1916, the engine was assigned the designation C.III (C for Conrad) by the German military.
Due to insufficient production capacity at the Deutsche Motorenbau-Gesellschaft, the engine was produced by the Nationale Automobil Gesellschaft (NAG).
C3, C-3, C.3, C03, C.III or C-III may refer to: