| Post: | Assistant Chief |
| Body: | the Air Staff |
| Flag: | Ensign of the Royal Air Force.svg |
| Flagcaption: | Ensign of the Royal Air Force (ACAS Command Flag) |
| Incumbent: | Air Vice-Marshal Suraya Marshall |
| Incumbentsince: | June 2024 |
| Department: | Ministry of Defence |
| Style: | Air Vice-Marshal |
| Member Of: | Air Force Board Civil Aviation Authority Board |
| Reports To: | Chief of the Air Staff |
| Appointer: | King Charles III |
| Formation: | c. April 1938 |
| First: | Air Chief Marshal Sir Anthony Skingsley |
| Abbreviation: | ACAS |
| Website: | Official website |
The Assistant Chief of the Air Staff (ACAS) is a senior appointment in the Royal Air Force. The current ACAS is Air Vice-Marshal Suraya Marshall.
The post was originally established circa February 1938, but without being made a member of the Air Council.[1]
The ACAS post was re-established in 1985 by eliminating the Vice Chief of the Air Staff and combining the Policy and Operations two star assistant chiefs. In 1992, ACAS became a member of the Air Force Board. The ACAS is responsible for "assisting the Chief of the Air Staff in generating a balanced and integrated Royal Air Force capability and for maintaining the fighting effectiveness and morale of the Service including the development of policy."[2] One of the many duties of the ACAS is to sit on the board of the Civil Aviation Authority as a non-executive member.[3]