Josef Ludvík František Ressel (in Czech) or Joseph Ludwig Franz Ressel (in German) or Josip Ressel (in Slovenian and Croatian) (June 29, 1793- October 9, 1857) was a Austrian forest warden and the inventor of the ship's propeller.
Ressel was born in Chrudim, Bohemia. His father was German and his mother Czech. He studied in Linz and Vienna and worked as a forest engineer in Motovun, Istria (modern-day Croatia) for the Austrian Government. He worked in Kostanjevica on the Krka river (modern-day Slovenia then Austrian Empire) where he tested his ship propellers for the first time. 1821 he was transferred to Trieste (modern-day Italy), the biggest port of the Austrian Empire where his tests were successful. He was awarded the propeller patent in 1827. He modified a small steam-powered boat Civeta by 1829 and test-drove it in the Trieste harbor at six knots before the steam conduits exploded. Because of this misfortune, the police banned further testing.
As early as 1804, the American John Fitch is credited with a screw propeller, which was unsuccessful. In 1836, the Englishman Francis Pettit Smith tested a screw propeller similar to Ressel's. The first cross-Atlantic journey of a ship powered by a screw-propeller was in 1839, with Ressel's screw improved by the Swedish engineer John Ericsson. The propeller screw design stabilized in the 1880s.
Among other Ressel's inventions are pneumatic post and ball and cylinder bearings. He was granted numerous patents during his life.