Ivar Vidfamne (or Ívarr inn víðfaðmi; English exonym Ivar Widefathom; Danish Ivar Vidfadme – in Norwegian and Danish the form Ivar Vidfavne is sometimes used as an alternative form) was a semi-legendary king of Sweden, who originated in Scania. He apparently died circa 700 CE, in Karelia, at a place called Karjálabotnar (Finnish Karjalanpohja), which may have been the modern Kurkiyoki (Russian Куркиёки; Finnish Kurkijoki; Swedish Kronoborg), in the Lakhdenpokhsky District (Finnish Lahdenpohja) of Russia.

12th and 13th century sources like Heimskringla and Hervarar saga, attributed to Ivar Vidfamne kingship of a wider empire that included parts of Norway, Saxony and England. However, no such figure was mentioned in medieval Saxon or English sources regarding the 8th and 9th centuries.