The Dornier Do 31 was an experimental vertical takeoff and landing (VTOL) jetpropelled transport designed and produced by West German aircraft manufacturer Dornier.

The development of the Do 31 was motivated principally by heavy interest expressed by the German Air Force in the acquisition of short takeoff and vertical landing aircraft (STOVL)capable aircraft. Such ambitions received a further boost from the issuing of NATO specification NBMR4, which called for a VTOLcapable tactical support aircraft that would be operated in conjunction with the EWR VJ 101, a West German VTOL strike aircraft designed under the NATO contract of BMR3.

A total of three aircraft, two flightcapable and one static airframe, were constructed and used for testing. On 10 February 1967, the Do 31 performed its maiden flight; the first hovering flight of the type took place during July 1967.