Mewstone is an oval 13.1 ha island, composed of muscovite granite, with steep cliffs and a small flat summit. It is part of the Pedra Branca Group, lying 12 km southeast of Maatsuyker Island, and 22 km off the south coast of Tasmania in south-eastern Australia. Its highest point is 150 m asl. Although it is sometimes referred to as Mewstone Island or The Mewstone, its official name is simply Mewstone. It is part of the Southwest National Park and the Tasmanian Wilderness World Heritage Site and is known for its inaccessibility, unusual shape and abundant bird life.