Temporal range: Miocene – Late Pleistocene
An artist's illustration of Megalibgwilia ramsayi
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Monotremata
Family: Tachyglossidae
Genus: Megalibgwilia
Griffiths, Wells and Barrie, 1991
Referred species
  • Megalibgwilia ramsayi (Owen, 1884)
  • Megalibgwilia robusta (Dun, 1896)

Megalibgwilia is a genus of large echidnas 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 Megalibgwilia ramsayi in 1884. Complete skulls and postcranial fossils have since been described. A second species, Megalibgwilia robusta, was described in 1896 by Australian paleontologist William Sutherland Dun.

Although they are sometimes commonly referred to as giant echidnas, Megalibgwilia species are thought to have been similar in size to the contemporary western long-beaked echidna, but with slightly longer forearms. They were smaller than a large species known from fossils in Australia, Zaglossus hacketti. Megalibgwilia ramsayi fossils have been found in deposits across mainland Australia and on Tasmania. Megalibgwilia robusta has only been found in New South Wales. Megalibgwilia was probably an insect-eater, like the short-beaked echidna, rather than a worm-eater like members of Zaglossus.

Megalibgwilia robusta is the oldest known echidna and the only known Miocene species.