Stefan Ossowiecki (Moscow, 22 or 26 August 1877 – Warsaw, 5 August 1944) was a Polish engineer who was, during his lifetime, promoted as one of Europe's best-known psychics. Two notable persons who credited his claims were pioneering French parapsychologist Gustav Geley and Nobel Prize-winning physiologist Charles Richet, who called Ossowiecki "the most positive of psychics."