Royal Navy Submarines
Nuclear-powered Ballistic Missile Submarines (SSBN)
Check out our 2022 comparative overview post on World ballistic missile boats.
Vanguard Class LOA 492′ / 150 m TDISP 15,900 tons submerged (4 active, service since 1993) 16 MIRV-equipped SLBM tubes/boat
Resolution Class LOA 425′ / 129.5 m TDISP 8,400 tons submerged (4 retired, service 1968-1996) units all stored at Rosyth, pending disposal solution. 16 SLBM tubes/boat
Fleet submarines (Nuclear powered) SSN
Astute Class LOA 318′ / 96.9 m TDISP 7,400 tons submerged (7 planned, 4 in service, service since 2010)
HMS Audacious S-122 (2020) 
Trafalgar Class LOA 280′ / 85.3 m TDISP 5,250 tons submerged (7 built, 2 active, service since 1983) 
Swiftsure class LOA 272′ / 82.9 m TDISP 4,900 tons submerged (6, all retired, service 1973-2010)
HMS Sovereign S-108 (1974-2006) laid up at Devonport. First Swiftsure class submarine laid up there. 
HMS Swiftsure S-126 (1973-1992) note lack of propulsor at stern, which rest of class had. Laid up at Rosyth.
Valiant AND Churchill classes LOA 285′ / 86.9 m TDISP 4,900 tons submerged. (5 retired, 1 preserved, rest laid up awaiting scrapping) classes very similar. Churchills were repeats of the Valiants with internal improvements
HMS Courageous S-50 (1971-1992) Museum Boat at Devonport. Falklands War veteran. 
HMS Conqueror S-48 (1971-1992) Laid up at Devonport. Falklands War veteran. Sank the Argentine cruiser ARA General Belgrano. 
HMS Churchill S-46 (1968-1991) Laid up at Rosyth awaiting disposal. 
HMS Dreadnought S101 (1963-1980) LOA 266′ / 81.1 m TDISP 4,000 tons submerged. First British nuclear submarine. Laid up at Rosyth awaiting disposal. 
Attack Submarines (Diesel Electric) SS
For Upholder Class, see Canadian Victoria Class
Oberon Class LOA 295′ / 89.9 m TDISP 2,400 tons submerged (27 built, service with 5 navies, all retired) See also Australian submarines, Brazilian Submarines, Canadian Submarines, Chilean Submarines, for other Oberons.
HMS Ocelot S-17 (1964-1991) Museum boat Chatham Historic Dockyard since 1992.
HMS Otus S-18 (1963-ca. 1992) Museum boat in Sassnitz, Germany. 
HMS Onyx S-21 (1967-1991) Museum Boat at Birkenhead on display with Warship Preservation Trust, until it went bankrupt. Displayed at Barrow-in-Furness until 2014, scrapped. Falklands War veteran. 
HMS Opossum S-19 (1964-1993) and HMS Oracle S-16 (1963-1993) both scrapped late 90s early 2000s at Pounds Marine, Portsmouth.
HMS Alliance P-417 (1947-1979) Amphion Class LOA 281′ / 85.6 m TDISP 1,600 tons submerged. Museum ship at Royal Navy Submarine Museum, Gosport.
The Searchers 