The Sikorsky SH-3 Sea King (company designation S-61) is a twin-engined anti-submarine warfare (ASW) helicopter. It served with the United States Navy and other forces, and continues to serve in many countries around the world.

The Sea King has been built under license in Italy, Japan, and the United Kingdom.

The British license-built version of the American Sikorsky S-61 helicopter is built by AgustaWestland.

The aircraft differs considerably from the American version, with British-built Gnome engines, British made anti-submarine warfare systems and a fully computerised control system.

The Sea King was also produced as the Commando troop transport version for export.

Westland Helicopters signed a licence agreement with Sikorsky in 1969 to use the airframe and rotor system of the Sikorsky Sea King to meet a British Royal Navy requirement for an Anti-submarine warfare helicopter to replace the Westland Wessex. The prototype and pre-production aircraft were built using Sikorsky-built components. The first Westland-built aircraft, the first production aircraft for the Royal Navy designated the Sea King HAS1, first flew on the 7 May 1969 and was delivered to the navy in the same year.

The last Sea King to be built by Westland was at Yeovil in 1990 and the last of the Royal Navy Sea King ASW helicopters was retired in 2003, being replaced by the AgustaWestland Merlin HM1. The Airborne Surveillance and Area Control (ASaC) or Airborne Early Warning (AEW) variant is expected to be replaced in time for the two Queen Elizabeth-class aircraft carriers. The types in contention are a Merlin derivative, a V-22 Osprey variant or a derivative of the E-2C Hawkeye. The HC4 commando variant is also expected to be replaced within the next decade along with Search and Rescue variants. 330 were produced in total.