Mewstone is an unpopulated island, composed of muscovite granite, located close to the south coast of Tasmania, Australia.

The 13.1-hectare (32-acre) island has steep cliffs and a small flat summit and is part of the Pedra Branca group, lying 12 kilometres (7.5 mi) southeast of Maatsuyker Island, and 22 kilometres (14 mi) off the south coast of Tasmania.

Mewstone comprises part of the Southwest National Park and the Tasmanian Wilderness World Heritage Site.

[1][2] The highest point of the island is approximately 150 metres (490 ft) above sea level.

It is likely that Mewstone was named after the Great Mew Stone, an island about 8 kilometres (5.0 mi) south-southeast of Furneaux's birthplace in Plymouth, United Kingdom.