Merimbun Lake is the largest natural lake in Brunei. It is located near Mukim Rambai in the Tutong District, about 70 km from the capital, Bandar Seri Begawan. The S-shaped lake is located 27 km from Tutong Town and it is surrounded by the 7800-hectare Tasek Merimbun Heritage Park.

Tutong District or simply Tutong is one of the four districts of Brunei. It has an area of 1,166 square kilometres (450 sq mi); the population was 48,313 in 2016. The administrative town is Pekan Tutong. It is home to Tasek Merimbun, the country's largest natural lake.