Malaysia is the only country that borders the nation of Negara Brunei Darussalam or most commonly known as Brunei. To be exact, the state which borders Brunei is Sarawak which is one of the two states of Malaysia located on the island of Borneo. However, since we are talking about which country borders Brunei, then the right answer is Malaysia.
Sarawak has a total area of 124,450 square kilometers and a total population of more than 120 thousand people. Brunei, on the other hand, has a total area of 5,765 square kilometers and a population of more than 417 thousand people. Aside from the land area bordering Brunei, the South China Sea coastline also borders the state. The Malaysia-Brunei border stretches 481.3 kilometers from east to west of Brunei and Malaysia.