HMS Argus was a British aircraft carrier that served in the Royal Navy from 1918 to 1944. She was converted from an ocean liner that was under construction when the First World War began, and became the first example of what is now the standard pattern of aircraft carrier, with a full-length flight deck that allowed wheeled aircraft to take off and land. After commissioning, the ship was heavily involved for several years in the development of the optimum design for other aircraft carriers. Argus also evaluated various types of arresting gear, general procedures needed to operate a number of aircraft in concert, and fleet tactics. The ship was too top-heavy as originally built and had to be modified to improve her stability in the mid-1920s. She spent one brief deployment on the China Station in the late 1920s before being placed in reserve for budgetary reasons.
Argus was recommissioned and partially modernised shortly before the Second World War and served as a training ship for deck-landing practice until June 1940. The following month she made the first of her many ferry trips to the Western Mediterranean to fly off fighters to Malta; she was largely occupied in this task for the next two years. The ship also delivered aircraft to Murmansk in Russia, Takoradi on the Gold Coast, and Reykjavík in Iceland. By 1942, the Royal Navy was very short of aircraft carriers and Argus was pressed into front-line service despite her lack of speed and armament. In June, she participated in Operation Harpoon, providing air cover for the Malta-bound convoy. In November, the ship provided air cover during Operation Torch, the invasion of French North Africa, and was lightly damaged by a bomb. After returning to the UK for repairs, Argus was used again for deck-landing practice until late September 1944. In December, she became an accommodation ship and was listed for disposal in mid-1946. Argus was sold in late 1946 and scrapped the following year.