William Peter Durtnall (1873–1947), M.I.Mar.E., M.I.Auto.E., M.I.Loco.E, was a British electrical engineer and inventor, and a captain in the Royal Air Force. He was involved in both marine and locomotive engineering and invented a thermoelectric engine patented as the "Paragon". He transferred from the Royal Navy Volunteer Reserve to a temporary commission as a captain in the Royal Air Force in April 1918.