Her Majesty's Naval Base (HMNB) Clyde is one of three operating bases in the United Kingdom for the Royal Navy (the others being HMNB Devonport and HMNB Portsmouth). It is the service's headquarters in Scotland and is best known as the home of the United Kingdom's strategic nuclear deterrent, in the form of nuclear submarines armed with Trident missiles. HMNB Clyde lies on the eastern shore of Gare Loch in Argyll and Bute, Scotland, to the north of the Firth of Clyde and 25 mi (40 km) west of the city of Glasgow. The submarine base encompasses a number of separate sites, the primary two being: Faslane, 25 miles from Glasgow; RNAD Coulport, beside Loch Long, 8 mi (13 km) west of Faslane.
Faslane is also a Defence Equipment and Support site, operated in dual site organisation with Great Harbour, Greenock, by Babcock Marine, and managed by Serco Denholm. Faslane Naval Base, situated on the Gare Loch, and the RN Armaments Depot Coulport on Loch Long, are the primary components of HM Naval Base Clyde. The Naval shore establishment at Faslane is HMS Neptune, Naval personnel appointed to the base who do not belong to a sea-going vessel make up Ship's Company. Both the Gareloch and Loch Long are sea lochs extending northwards from the Firth of Clyde. The base serves as home base to the United Kingdom's fleet of Vanguard-class nuclear-powered and nuclear-armed submarines, as well as conventionally-armed nuclear powered submarines, supported by the Fleet Protection Group Royal Marines.