Sea Dart, or GWS.30 was a Royal Navy surface-to-air missile system designed in the 1960s and entering service in 1973. It was fitted to the Type 42 destroyers, the sole Type 82 destroyer and the Invincible-class aircraft carriers. Originally developed by Hawker Siddeley, the missile was built by British Aerospace after 1977.

The missile was withdrawn from service in 2012, as the ageing system no longer met modern air defence requirements. The final operational launch took place on 13 April 2012, when HMS Edinburgh (D97) conducted the last Sea Dart firing during a major exercise off the coast of Scotland, bringing an end to the system’s 40-year service history.

Britain's first naval surface-to-air missile was GWS1 Seaslug, which entered service in 1963. This used beam riding guidance which offered limited accuracy and was effective only against slower targets. The need for a higher performance system was identified even as Seaslug entered service.

Bristol Aerospace, which had recently introduced the ramjet-powered Bloodhound missile for the RAF, proposed a new ramjet-powered design, while the British Aircraft Corporation (BAC) offered a shorter-range rocket-powered design. The Admiralty requested a proposal combining BAC's layout with Bristol's engine, resulting in the Sea Dart. Compared to Seaslug, Sea Dart was faster, had greater range, and its semi-active radar homing guidance was more accurate and capable of engaging supersonic targets. Following the Falklands War, further upgrades extended its range to 80 miles (130 km).

The system achieved nine confirmed successful combat engagements, including six aircraft, a helicopter, and an anti-ship missile. This included the first instance of a missile destroying another missile in combat. An additional helicopter was destroyed in a friendly fire incident during the Falklands War.

From the immediate post-Second World War era, the Royal Navy sought a general-purpose weapon suitable for arming smaller ships. Experience with German glide bombs during the war showed the need for a medium-range surface-to-air missile capable of destroying carrier-based bombers before they could reach a range for launching glide bombs. As such a system would occupy space normally used for a dual-purpose gun, it was also intended to have a secondary anti-ship capability, although this requirement was later reduced.

Research and trials in the 1950s produced the Seaslug system. While effective against first-generation strike aircraft, its performance against faster aircraft and anti-ship missiles was limited, and its size made it unsuitable for frigate-sized ships. A high-performance gun concept, the DACR (direct-action, close-range), was considered, but calculations showed it would be ineffective against future manoeuvring anti-ship missiles.

In October 1960, the Navy launched the Small Ship Integrated Guided Weapon System project to fill this need, SIGS for short. This called for a weapon small enough to be carried on a 3,000 ton frigate and able to attack bombers, anti-shipping missiles, and other ships up to frigate size. Seaslug had taken much longer to develop than expected and was a very costly, ongoing program. There was some concern that development of a new system should not commence before Seaslug was in service. A review by the Defence Research Policy Committee agreed with the Navy that the new design represented an entirely new class of weapon and that development should be undertaken immediately.