Brunei, officially State of Brunei, and formally Brunei Darussalam, is a country in Southeast Asia, situated on the northern coast of the island of Borneo. Apart from its coastline on the South China Sea, it is completely surrounded by the Malaysian state of Sarawak, with its territory bifurcated by the Sarawak district of Limbang. Brunei is the only sovereign state entirely on Borneo; the remainder of the island is divided between its multi-landmass neighbours of Malaysia and Indonesia. As of 2023, the country had a population of 455,858, of whom approximately 150,000 resided in the capital and largest city of Bandar Seri Begawan. Its official language is Malay and Islam is the state religion of the country, although other religions are nominally tolerated. The government of Brunei is an absolute monarchy ruled by the Sultan of Brunei, and it implements a fusion of English common law and jurisprudence inspired by Islam, including sharia.

Borneo is the third-largest island in the world, with an area of 748,168 km2 (288,869 sq mi). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda Islands, located north of Java, west of Sulawesi, and east of Sumatra.