Flight Sergeant (FS or Flt Sgt) is a non-commissioned rank in the Royal Air Force, above Chief Technician and below Warrant Officer. It is equivalent to a Staff Sergeant in the British Army and has a NATO rank code of OR-7. The rank insignia is three downward pointing chevrons below a crown. Flight sergeants are usually addressed as Flight and are never addressed by the junior rank of Sergeant.

The rank was formerly used in the Royal Flying Corps and passed to the RAF on its formation in 1918. RFC flight sergeants wore a four-bladed propeller between the chevrons and the crown.

Between 1950 and 1964, the rank of Chief Technician was equivalent to flight sergeant and was held instead of it by technicians, but now chief technician is a junior rank (still only held by technicians), although classified by NATO in the same grade.

On 1 July 1946, aircrew flight sergeants were redesignated Aircrew I and replaced their chevrons with three six-pointed stars within a wreath and surmounted by an eagle and a crown. This proved unpopular however, and in 1950 they reverted to their old rank and badge, although they have worn an eagle between chevrons and crown ever since.