Map - Brunei-Muara District (Daerah Brunei dan Muara)

Brunei-Muara District (Daerah Brunei dan Muara; Jawi: برونائی-موارا ضلع ) or simply Brunei-Muara is one of the four districts of Brunei. It has the smallest area among the four districts, with 571 km2, 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.

The district borders the South China Sea to the north, Brunei Bay to the east, Limbang District in the Malaysian state of Sarawak to the south, and Tutong District to the west.

The Brunei River is the sole primary river and only flows in the district. It begins in the south-western part and flows north-eastwards which finally discharges into the Brunei Bay.

There are several in-bay and coastal islands in the Brunei Bay belonging to the Brunei-Muara district. These islands include Pulau Muara Besar, Pulau Salar, Pulau Simangga Besar, Pulau Bedukang, Pulau Kaingaran, Pulau Chermin, Pulau Pepatan, Pulau Baru-Baru, Pulau Berbunut, Pulau Sibungor, Pulau Ranggu and Pulau Berambang. There is one man-made "island" off the coast of Mukim Serasa that is actually a spit turned into an "island" called Tanjong Pelumpong (Pelumpong Spit). There are two off-shore islands off the coast of the Brunei-Muara district in the South China Sea, Pulau Pungit, off the coast of Sengkurong and Pulau Pelong-Pelongan, off the coast of Mukim Serasa.