Bougainville Island is the main island of the Autonomous Region of Bougainville, which is part of Papua New Guinea. Its land area is 9,300 km². The highest point is Mount Balbi, on the main island, at 2,715 m.
The much smaller Buka Island, c. 500 km², lies to the north, across the 400–500 m wide Buka Strait.
