No. 3 Squadron is a Royal Australian Air Force (RAAF) fighter squadron, headquartered at RAAF Base Williamtown, near Newcastle, New South Wales. Established in 1916, it was one of four combat squadrons of the Australian Flying Corps during World War I, and operated on the Western Front in France before being disbanded in 1919. It was re-established as a permanent squadron of the RAAF in 1925, and during World War II operated in the Mediterranean Theatre. The Cold War years saw the squadron disbanded and re-raised twice. It was based at RAAF Butterworth during the Malayan Emergency and the Indonesia–Malaysia Konfrontasi. Equipped with McDonnell Douglas F/A-18 Hornet multi-role fighters from 1986, the squadron deployed to Diego Garcia in 2002 to provide local air defence, and the following year contributed aircraft and crews to the invasion of Iraq as part of Operation Falconer. In April 2016, it deployed to the Middle East as part of the military intervention against ISIL. The squadron began re-equipping with Lockheed Martin F-35 Lightning II multi-role fighters in 2018.

The Royal Australian Air Force (RAAF) is the principal aerial warfare force of Australia, a part of the Australian Defence Force (ADF) along with the Royal Australian Navy and the Australian Army. Constitutionally the Governor-General of Australia is the de jure Commander-in-Chief of the Australian Defence Force. The Royal Australian Air Force is commanded by the Chief of Air Force (CAF), who is subordinate to the Chief of the Defence Force (CDF). The CAF is also directly responsible to the Minister for Defence, with the Department of Defence administering the ADF and the Air Force.