Special Air Service or SAS is a corps of the British Army constituted on 31 May 1950. They are part of the United Kingdom Special Forces (UKSF) and have served as a model for the special forces of many other countries all over the world. The SAS together with the Special Boat Service (SBS), Special Reconnaissance Regiment (SRR), and the Special Forces Support Group (SFSG) form the UKSF under the command of the Director Special Forces.

The Special Air Service presently comprises 22 Special Air Service Regiment of the Regular Army, 21 Special Air Service Regiment and 23 Special Air Service Regiment from the Territorial Army. It is tasked with special operations in wartime, and primarily counter-terrorism in peacetime.