Megalibgwilia is a genus of echidna known only from Australian fossils that incorporates the oldest known echidna species. It lived during the Pleistocene, becoming extinct about 50,000 years ago. Megalibgwilia was first described from a broken left humerus by Richard Owen when he identified M. ramsayi in 1884. Complete skulls and postcranial fossils have since been described. A second species, M. robusta, was described in 1896 by Australian paleontologist William Sutherland Dun. M. robusta is the oldest known echidna and the only known Miocene species.