Kathleen Island is a steeply cliffed island that lies within Port Davey, an oceanic inlet, located in the south west region of Tasmania, Australia.

[1] The island has an area of approximately 11.35 hectares (28.0 acres) and is contained with the Southwest National Park, part of the Tasmanian Wilderness World Heritage Site and the Port Davey/Bathurst Harbour Marine Nature Reserve.

[3][4] Kathleen island is part of the Port Davey Islands Important Bird Area, so identified by BirdLife International because of its importance for breeding seabirds.

[5] Most of the island is covered by thick scrub and rainforest.

Burrowing seabirds have caused erosion in places.