Belait District, or simply Belait, is the largest as well as the westernmost district in Brunei. It has an area of 2,727 square kilometres (1,053 sq mi) and the population of 69,062 as of 2016. The administrative town is Kuala Belait, located at the mouth of the Belait River. The district is commonly associated with the oil and gas industry of the country, mainly concentrated near the town of Seria.

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.