The Ministry of Defence Brunei Darussalam, officially abbreviated as MinDef, is a cabinet-level ministry of the Government of Brunei. It is responsible for the national security and its military forces within the sultanate of Brunei Darussalam; the latter collectively known as the Royal Brunei Armed Forces (RBAF); Angkatan Bersenjata Diraja Brunei, (ABDB). MinDef is Brunei's ministry of defence; and was established on 1 January 1984, when Brunei Darussalam achieved independence from the United Kingdom. The Ministry of Defence leadership presently consists of a minister ; its incumbent is the Sultan of Brunei, Hassanal Bolkiah, who is also the Supreme Commander of the RBAF / ABDB. A deputy minister is second-in-command at the Ministry of Defence.

The Royal Brunei Armed Forces (RBAF); Malay: Angkatan Bersenjata Diraja Brunei, (ABDB), is the collective term for all of the military forces or service branches of the sultanate of Brunei Darussalam. The RBAF consists of three primary military branches; the Royal Brunei Land Force, the Royal Brunei Navy, and the Royal Brunei Air Force.