Rudolf Erren

Rudolf Arnold Erren (15 August 1899 – death date unknown) was a German engineer and inventor who did important work on the use of hydrogen fuels in the early 20th century. He had several patents, developed the Erren engine, and his work was "apparently the earliest reported use of hydrogen-engine supercharging of any kind." One of Germany's World War II U-boats supposedly had a hydrogen engine designed by Erren.

Erren was born in Prussia, served in both the German Army and Air Force during World War I, then became a police officer, and was "acquitted of a charge of murdering a superior officer." Erren was interned in Canada by the British during World War II and repatriated 28 October 1945. He may have applied for British naturalisation in 1946. He returned to Germany and remarried.