The East Kangaroo Island, part of the Big Green Group within the Furneaux Group, is a 157-hectare (390-acre) unpopulated limestone island with granite outcrops and dolerite dykes, located in the Bass Strait, west of the Flinders Island, in Tasmania, in south-eastern Australia.

[1] Prior to its declaration as the East Kangaroo Island Nature Reserve, the island was previously used to graze sheep, with overgrazing causing severe erosion.

[3] Recorded breeding seabird and wader species are little penguin, short-tailed shearwater, Pacific gull, silver gull, sooty oystercatcher and crested tern.

Cape Barren geese also breed on the island.

The only terrestrial mammal is the introduced House mouse.