Royal Naval Air Station Yeovilton, commonly referred to as RNAS Yeovilton, (IATA: YEO, ICAO: EGDY) (HMS Heron) is an airbase of the Royal Navy, sited a few miles north of Yeovil, in the English county of Somerset.

In 1939, the Admiralty Air Division commandeered 417 acres (169 hectares) of the land, and work began on the construction of the site.

[2] After the end of the war, Yeovilton became one of the main demobilisation centres for the Royal Navy, with many of the men helping to refurbish the runways while they stayed at the base.

The base remained as the home of the Commando Helicopter Squadrons, using the Wessex HU5 and later the Sea King HC4, and the fixed wing Fleet Requirements and Aircraft Direction Unit (FRADU), and became the main shore base for the Navy's fleet of Sea Harrier FRS1 (and later, FA2).

[4] In the mid 1980s, Defence Estates announced that many of the Royal Navy ratings married quarters at RNAS Yeovilton were surplus to requirements.

(Note that while 'HMS' is typically a designation for a ship, the Royal Navy also used it for land-based establishments, known as a 'stone frigate'.)

In July 2006, Sea King HC4 helicopters from RNAS Yeovilton were deployed to Cyprus on Operation Highbrow to assist with the evacuation of British citizens from Lebanon.

[9] The Strategic Defence and Security Review 2010 recommended that in order to replace the Navy's ageing Westland Sea King HC4's which formed the Commando Helicopter Force at Yeovilton, the RAF's AgustaWestland AW101 Merlin fleet should be transferred from the Royal Air Force to the Royal Navy's Fleet Air Arm.

[11][12] The last phase of the transition occurred when 845 NAS departed Benson for Yeovilton on 16 June 2016, bringing nearly 15 years of RAF Merlin operations to a close.

[13][14] The AgustaWestland AW159 Wildcat HMA2 began replacing the Westland Lynx HMA8 when the first production aircraft arrived at Yeovilton in January 2013.

In order to allow the Army Air Corps to locate their Wildcat helicopters and 750 personnel at Yeovilton, extensive redevelopment of the station began in 2014.

Known as Project WINFRA, the work involves eight separate contracts worth a total of £150 million and was undertaken by Mott McDonald and Carillion.

[24] The Royal Navy Historic Flight (RNHF) was disbanded in March 2019, previously operating at RNAS Yeovilton since 1972.

[26] With the aircraft having now been transferred to the civilian register, displays are now funded from charity events run by the Fly Navy Heritage Trust.

The station operates over 100 aircraft, and is staffed by around 1675 service and 2000 civilian personnel, including Ministry of Defence (MOD) employees and permanent contractors.

727 Naval Air Squadron operate the Grob Tutor T1 in the grading and elementary flying training role.

The Merlin HC3/3A fleet is currently undergoing an upgrade to HC4 and HC4A, to ensure the aircraft are fully capable of deploying in a maritime / amphibious role.

[32] The differences between the remaining HC3 and (former Denmark-bound) HC3A will be almost eliminated in the HC4/4A upgrade, known as the Merlin Life Sustainment Programme (MLSP).