Buka Island is the second-largest island in the Autonomous Region of Bougainville, in eastern Papua New Guinea. It is in Buka Rural LLG of North Bougainville District, with the Autonomous Region's and district's capital city of Buka on the island.

The island is separated by the narrow Buka Passage from the northwestern coast of Bougainville Island, and has an area of approximately 500 km² (190 sq mi). Buka, Bougainville Island and the Tabar Islands and their surrounding waters are identified as being part of the Solomon Archipelago terrestrial ecoregion and marine ecoregion.

Buka was first occupied by humans in the Paleolithic period, with evidence for human habitation at Kilu Cave some 30,000 years ago.

British, Australian and American whaling ships visited the island in the nineteenth century for food, water and wood. The first on record was the Eliza in 1806, and the last known visit was by the Palmetto in 1881.

The present inhabitants speak languages that are from the eastward push of Austronesian languages of the Lapita Culture complex, some 2,700 years ago.

In 1899 the German Empire laid claim to the island, annexing it into German New Guinea.

Buka Island was occupied by Japanese troops during World War II, and it was the site of important Japanese airfields that were considered strategic by the allies.

Although the island was bombed by allied air forces and warships, allied armies never fought in Buka. After holding out for years on poor supplies, the Japanese surrendered in 1945 when allied troops were approaching the Selau peninsula on nearby Bougainville.^{[citation needed]}