Bougainville ( BOH-gən-vil; Tok Pisin: Bogenvil), officially the Autonomous Region of Bougainville (Tok Pisin: Otonomos Region bilong Bogenvil), is an autonomous region in Papua New Guinea. The largest island is Bougainville Island, while the region also includes Buka Island and a number of outlying islands and atolls. The provisional capital is Buka, on Buka Island.
In 2024, the region had an population of 367,093. The lingua franca of Bougainville is Tok Pisin, while a variety of Austronesian and non-Austronesian languages are also spoken. The region includes several Polynesian outliers where Polynesian languages are spoken. Geographically, the islands of Bougainville and Buka form part of the Solomon Islands archipelago, but they are politically separate from the independent country of Solomon Islands. Historically, Bougainville and Buka, together with the islands of Choiseul, Santa Isabel, the Shortlands, and Ontong Java, which are all now part of the country of Solomon Islands, formed the German Solomon Islands Protectorate, the geographical area later being referred to as the North Solomon Islands.