Thaddeus of Warsaw is an 1803 novel written by Jane Porter. It comprises four volumes. The story was derived from eyewitness accounts of British soldiers and Polish refugees fleeing the failed revolts against the foreign occupation of Poland in the 1790s. It was thought by Olga S. Phillips (1940), author of Isaac Nathan's biography, that the character of Thaddeus was based on Nathan's father Menachem Mona Polack (Moses Monash the Pole) who was thought to be the illegitimate son of King Stanisław August Poniatowski and his Jewish mistress Elżbieta Szydłowska. Phillips claims that Jane Porter used to call Isaac Nathan 'Thaddeus' when touching his face as a child.