Hans von Ohain, German-American physicist and engineer (d. 1998)
Hans Joachim Pabst von Ohain (14 December 1911 – 13 March 1998) was a German physicist, engineer, and the designer of the first operational jet engine. His first test unit ran on externally supplied hydrogen in March 1937, and it was a later development that powered the world's first flyable all-jet aircraft, the prototype of the Heinkel He 178 (He 178 V1) in late August 1939. In spite of these early successes, other German designs quickly eclipsed Ohain's, and none of his engine designs entered widespread production or operational use.

Ohain started to develop his first turbojet engine designs independently during the same period that Frank Whittle was working on his own similar designs in Britain, and their turbojet designs are said by some to be an example of simultaneous invention. However, Frank Whittle was already working on his design in the late 1920s and openly patented the design in 1930, a full seven years before Ohain's design ran. The core of Ohain's first jet engine, the Heinkel HeS 1, which he described as his 'hydrogen test engine' was run 'in March or early April' according to Ohain (although Ernst Heinkel's diaries record it as September 1937) but it was not self-sustaining, requiring externally supplied hydrogen. The engine required modifications to cure overtemperature problems and to fit a fuel system to enable it to run self-contained on liquid fuel which was achieved in September 1937, . Ohain's jet engine was the first to fly operationally within the Heinkel He 178 aircraft in 1939, which was followed by Whittle's engine within the Gloster E.28/39 in 1941. Operational jet fighter aircraft from both Germany and Britain entered operational use virtually simultaneously in July, 1944. After the war the two men met and became friends.