Megalibgwilia is a genus of echidna known only from Australian fossils that incorporates the oldest-known echidna species. It is also the only extinct echidna genus. The genus ranged from the Miocene until the late Pleistocene, becoming extinct about 50,000 years ago. Megalibgwilia species were more widespread in warmer and moist climates. The extinction can be attributed to increasing aridification in Southern Australia. M. robusta is the oldest-known echidna and the only known Miocene species.