Airfield Defence Guards (ADG) are a mustering of the Royal Australian Air Force (RAAF) that are dedicated to the security and ground defence of airbases and other military aviation assets. Other duties include instructing other RAAF personnel, in skills such as the handling of small arms and infantry tactics.

The mustering's members, commonly known as "Adgies", are mostly employed in RAAF Security Force (SECFOR) squadrons. Previously a Direct-Entry role, the ADG mustering has since become a specialist role for SECFOR members and only after serving a minimum 12 months can be applied for, where applicants are invited to a course. The role of SECFOR squadrons is the protection of RAAF equipment, personnel, assets and facilities, by countering attacks by the enemy including their special forces, infantry, local banditry, guerilla's, terrorist's and other irregular military.

ADGs are commanded by Squadron Leaders (SQNLDR) and assisted by Flight Lieutenants (FLTLT) and Flying Officers (FLGOFF) who are commissioned officers known as Ground Defence Officers (GRDEFO) they receive initial training at the Australian Army's Royal Military College (RMC), Duntroon. Following graduation from RMC, GRDEFOs undertake the Army Regimental Officer Basic Course (Infantry) prior to RAAF-specific training at the RAAF Security and Fire School (RAAFSFS), at RAAF Base Amberley.

ADG are comparable to the British Royal Air Force Regiment, and the USAF Security Forces.

From 1929 the RAAF began to establish an Aerodrome Defence Scheme (ADS), primarily utilizing aircraft personnel to provide local defence of airfields, although it was initially limited in scope. Following the acquisition of the required equipment training began in 1931, including in both anti-aircraft and ground defence roles. Between 1931 and 1939 this also included exercises with the Army, during which Aerodrome Defence Sections defended an area against attacks by Australian Army units and RAAF aircraft. In 1939 it was directed that the scheme be expanded to include all units and stations.

While the RAAF did not face a significant ground threat in the first years of World War II, an Air Force Guard mustering was proposed in 1940. This mustering was to receive training in infantry tactics to defend RAAF bases against attack and would be modelled on the Royal Air Force Regiment. The idea never progressed and those recruited for the task were assigned to other mustering's. Following the bombing of Darwin in 1942 and ground attacks on Allied air bases, it was realised that the RAAF needed to defend its own airfields and that ground defence training was required for RAAF personnel.

Following a request to the Army, Lieutenant Colonel H.H. Carr was seconded to the RAAF from 2/22 Battalion AIF in May 1942. Further secondments of infantry officers and NCOs followed and the RAAF Defence School was established at Hamilton, Victoria in September of that year. The school commenced training Army and RAAF officers and NCOs as Aerodrome Defence Officers and Aerodrome Defence Instructors, who were then posted to RAAF units to deliver ground defence training.

In October 1942, the Security Guards Unit was formed at Livingstone Field, Northern Territory. All RAAF guards were posted to this unit, irrespective of where they were serving. The Security Guards Unit was charged with providing guards for operational bases both within Australia and overseas. Trainees were instructed in the employment of anti-aircraft guns, ground patrolling, scouting and hand-to-hand combat. At first the unit had a strength of 567 personnel, increasing to 943 by July 1943; in that year the unit moved to Darwin. The unit was renamed No. 1 Airfield Defence Squadron in April 1945.