[12] This naming reflects the town's geographical position at the mouth of the Belait River, where it empties into the South China Sea.

As with other kuala settlements, the location was likely chosen for its strategic significance, offering both defensive advantages and accessibility for trade and transportation along the river and coastal routes.

However, the discovery of oil in Labi convinced prospectors that further deposits might be found along the higher banks of the Belait River.

[14] Oil companies began concentrating their activities in the area, leading to the emergence of a thriving village in Kuala Belait by 1927.

At the time, it served as a port for transporting machinery crucial to oil prospecting, primarily managed by the British Malayan Petroleum Company (BMPC).

Despite this progress, the town was heavily bombed during World War II, leading to widespread destruction and the need to rebuild.

[23] As part of Operation Oboe Six, the Australian 9th Division arrived in Kuala Belait on 24 June 1945,[24] leading to the recapture of the port.

[25][26] Kuala Belait experienced significant growth during the 1950s and 1960s, driven by increased revenue from the booming oil industry.

[16] The discovery of the first offshore gas field, South West Ampa, located 13 kilometres (8.1 mi) off Kuala Belait in 1963, further boosted the town's growth.

In the 1990s, the coastal road from Muara to Kuala Belait was upgraded to a four-lane highway, further enhancing the town's infrastructure.

[36] The Kuala Belait supply base is located to the south of the wharf, and is the main point for logistics for Shell.

Initially, communication with the capital was challenging, as access by land required traveling along the beach between Kuala Belait and Tutong, where a road existed.

In 1931, the appointment of an assistant British Resident marked a turning point, although land connections with Brunei Town remained difficult.

The BMPC played a crucial role in enhancing road infrastructure, providing necessary improvements to support the growing immigrant population associated with the oilfields.

By 1938, the population of Kuala Belait had reached 5,000, with the BMPC being the largest employer in the district and continuing to invest in local infrastructure.

Initially, communication with the capital was primarily by sea and via Labuan, as the Belait River was closed for six months each year due to the monsoon, which hindered trade.

The BMPC contributed significantly to the development of water transport facilities by establishing wharves to facilitate the movement of materials and personnel to and from the oilfields.

Additionally, the Kuala Belait Boat Club organizses trips for sailing out to the open sea and visiting various nearby destinations.