Lake Rosebery is a man-made water reservoir located in the West Coast region of Tasmania, Australia. The lake is situated within the northern part of Tasmania's West Coast Range and is fed by the dammed Mackintosh and Murchison rivers. The reservoir is owned by Hydro Tasmania.
The Bastyan Dam across the Pieman River was built by the Hydro-Electric Commission in 1983. The dam created a reservoir, called Lake Rosebery, with a surface area ranging from , drawn from a catchment area of .
The lake is located near the village of .
The diverted Emu Bay Railway line and the Wee Georgie Wood Railway line run close to the lake.
In January 2025, 5,000 to 4,000 litres of oil entered the reservoir after a tank on private property leaked in heavy rain.