The Brunei–Muara District or simply Brunei-Muara is one of the four districts of Brunei. It has the smallest area among the four districts, with 571 square kilometres (220 sq mi), yet is the most populous, with 289,630 people as of 2016. Bandar Seri Begawan, the country's capital, is located in this district, which is also de facto the district's capital. It is also home to Brunei International Airport, the country's only international airport, as well as Muara Port, the main and only deep-water port in the country. The Brunei River flows within this district and is home to Kampong Ayer, the traditional historic settlement on stilts above the river.

Bandar Seri Begawan is the capital and largest city of Brunei. It is officially a municipal area with an area of 100.36 square kilometres (38.75 sq mi) and an estimated population of 100,700 as of 2007. It is part of Brunei-Muara District, the smallest yet most populous district which is home to over 70 per cent of the country's population. It is the country's largest urban centre and nominally the country's only city. The capital is home to Brunei's seat of government, as well as a commercial and cultural centre. It was formerly known as Brunei Town until it was renamed in 1970 in honour of Sultan Omar Ali Saifuddien III, the 28th Sultan of Brunei and the father of the current Sultan Hassanal Bolkiah.