HMS Dreadnought was a battleship of the British Royal Navy that revolutionised naval power. Her entry into service in 1906 represented such a marked advance in naval technology that her name came to be associated with an entire generation of battleships, the "dreadnoughts", as well as the class of ships named after her, while the generation of ships she made obsolete became known as "pre-dreadnoughts". She was the sixth ship of that name in the Royal Navy.

Admiral Sir John "Jackie" Fisher, First Sea Lord of the Board of Admiralty, is credited as the father of the Dreadnought. Shortly after he assumed office he ordered design studies for a battleship armed solely with 12-inch (305 mm) guns and a speed of 21 knots (39 km/h; 24 mph). He convened a "Committee on Designs" to evaluate the alternative designs and to assist in the detailed design process. One ancillary benefit of the Committee was that it would shield him, and the Admiralty, from political charges that they had not consulted leading experts before designing such a radically different battleship.

Dreadnought was the first battleship of her era to have a uniform main battery, rather than having a few large guns complemented by a heavy secondary battery of somewhat smaller guns. She was also the first capital ship to be powered by steam turbines, making her the fastest battleship in the world at the time of her completion. Her launch helped spark a major naval arms race as navies around the world, particularly the Kaiserliche Marine (German Imperial Navy) rushed to match her in the build-up to World War I.

Dreadnought did not participate in any of World War I's naval battles as she was refitting during the Battle of Jutland in 1916, the only time that British dreadnought battleships fired on their German counterparts during the war. However, she became the only battleship ever to sink a submarine when she rammed the SM U-29 when it unexpectedly broke the surface after firing a torpedo at another dreadnought in 1915. After Jutland, she was relegated to coast defence duties in the English Channel, only rejoining the Grand Fleet in 1918. She was reduced to reserve in 1919 and sold for scrap on 9 May 1921 for £44,000.

HMS Dreadnought revolutionised naval power when she entered service in 1906. Dreadnought represented such a marked advance in naval technology that her name came to be associated with an entire generation of battleships, the “dreadnoughts”, as well as the class of ships named after her, while the generation of ships she made obsolete became known as “pre-dreadnoughts”.

HMS Dreadnought (1906) Operators: Royal Navy Preceded by: Lord Nelson-class Succeeded by: Bellerophon-class Cost: £1,672,483 (excluding armament) (£133 million in today's pounds sterling) Built: 1905—1906 In service: 1906—1919 In commission: 1906—1919 Completed: 1 Scrapped: 1 Career Royal Navy Ensign Ordered: 1905 Builder: HM Dockyard, Portsmouth Laid down: 2 October 1905 Launched: 10 February 1906 Commissioned: 2 December 1906 Decommissioned: February 1919 Fate: Scrapped 1923 Displacement: 18,120 LT (18,410 t) (normal load) 20,730 LT (21,060 t) (deep load) Length: 527 ft (161 m) Beam: 82 ft 1 in (25.0 m) Draught: 29 ft 7.5 in (9.030 m) (deep load) Installed power: 23,000 shp (17,000 kW) Propulsion: 4 shafts, Parsons direct drive steam turbines 18 Babcock & Wilcox water-tube boilers Speed: 21 knots (39 km/h; 24 mph) Range: 6,620 nautical miles (12,260 km; 7,620 mi) at 10 knots (19 km/h; 12 mph) 2 Complement: 700—810 Armament: 5 x 2 — BL 12—inch Mark X guns 27 x 1 --12—pdr 18 cwt Mark I guns 5 x 18 inch (450 mm) torpedo tubes Armour: Belt: 4—11 in (102—279 mm) Deck: .75—3 in (19—76 mm) Barbettes: 4—11 in (102—279 mm) Turrets: 3—12 in (76—305 mm) Conning tower: 11 in (279 mm) Bulkheads: 8 in (203 mm)