The Dewoitine D.9 was a French monoplane fighter built by Dewoitine and built under licence in Italy as the Ansaldo AC.3.
The D.9 was a single-seat high-wing monoplane with a conventional landing gear and powered by a 3200NaN0 Gnome-Rhône 9Ab Jupiter radial engine. First flown in 1924 it was not accepted by the French Army being ranked sixth in the 1923 single-seat fighter competition. A small number of production aircraft were sold for export to Belgium and Yugoslavia and three were built from parts by EKW for the Swiss Air Force. The biggest achievement of the type was an order to licence-build 150 aircraft for the Italian Regia Aeronautica, built by Ansaldo as the Ansaldo AC.3. The type served into the 1930s with the Italian forces.