The Royal Navy battleship HMS Dreadnought was launched, representing such a marked advance in naval technology that her name came to be associated with an entire generation of battleships.

The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against France. The modern Royal Navy traces its origins to the English Navy of the early 16th century; the oldest of the UK's armed services, it is consequently known as the Senior Service.

HMS Dreadnought was a Royal Navy battleship, the design of which revolutionised naval power. The ship's entry into service in 1906 represented such an 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. Likewise, the generation of ships she made obsolete became known as pre-dreadnoughts. Admiral Sir John "Jacky" Fisher, First Sea Lord of the Board of Admiralty, is credited as the father of Dreadnought. Shortly after he assumed office in 1904, he ordered design studies for a battleship armed solely with 12 in (305 mm) guns and a speed of 21 knots. He convened a Committee on Designs to evaluate the alternative designs and to assist in the detailed design work.

The dreadnought was the predominant type of battleship in the early 20th century. The first of the kind, the Royal Navy's HMS Dreadnought, had such an effect when launched in 1906 that similar battleships built after her were referred to as "dreadnoughts", and earlier battleships became known as pre-dreadnoughts. Her design had two revolutionary features: an "all-big-gun" armament scheme, with an unprecedented number of heavy-calibre guns, and steam turbine propulsion. As dreadnoughts became a crucial symbol of national power, the arrival of these new warships renewed the naval arms race between the United Kingdom and Germany. Dreadnought races sprang up around the world, including in South America, lasting up to the beginning of World War I. Successive designs increased rapidly in size and made use of improvements in armament, armour, and propulsion throughout the dreadnought era. Within five years, new battleships outclassed Dreadnought herself. These more powerful vessels were known as "super-dreadnoughts". Most of the original dreadnoughts were scrapped after the end of World War I under the terms of the Washington Naval Treaty, but many of the newer super-dreadnoughts continued serving throughout World War II.