HMS Indomitable was a modified Illustrious class aircraft carrier. She was laid down in Barrow-in-Furness, on 10 November 1937, as war loomed ever closer. She was launched on 26 March 1940 and commissioned the following year in October.

She sailed to the West Indies in November 1941 for her maiden voyage. While there, Indomitable ran aground on a coral reef near Jamaica, though she returned to service soon afterwards. It has been suggested that this short delay proved fatal for British plans for Singapore. There were provisional plans that Indomitable was to join HMS Prince of Wales and HMS Repulse in the port of Singapore as part of a deterrent force, Force Orange, against Japanese aggression in the Far East. However, given that the aircraft carrier was in the vicinity of Jamaica, on November 3rd. 1941, it seems unlikely that Indomitable could really have reached Singapore in sufficient time to provide air cover for the battle fleet. For that to have been achieved, it would have been necessary to order the ship to proceed to Singapore, at an earlier date than November 3rd. In the event, the other two capital ships, designated Force Z, did not have adequate air cover, and were sunk by Japanese aircraft

In January 1942 Indomitable joined the Eastern Fleet based at Ceylon, where she ferried 48 RAF Hawker Hurricanes to Singapore.

After the fall of Hong Kong and Burma, Indomitable was redeployed. A new Eastern Fleet was established under the command of Admiral Sir James Somerville. Indomitable, and her sister-ship Formidable were the only modern aircraft carriers of the Fleet, and were a vital asset to the Allies in the Far East.

In April 1942 Somerville attempted to intercept the Japanese carrier strike force as they raided the Indian Ocean. Incomplete intelligence led him to abandon his ambush just hours before the Japanese force arrived. Over the next few days Indomitable was part of a force that attempted to intercept the Japanese fleet at night, where the slow, but radar equipped, British torpedo planes would have the best chance of a successful strike. Despite several days of searching no decisive action was achieved, and Somerville eventually withdrew his fast carriers to Bombay.  It was feared that the Japanese would themselves occupy Madagascar and use it as a submarine base to attack allied convoy routes in the Indian Ocean.

She participated  in Operation Pedestal, the largest convoy to supply the besieged island of Malta. This convoy comprised 14 cargo ships and an unprecedentedly large escort of 44 warships.  

During the operation Indomitable was hit by two 500 kg bombs and suffered three near misses; a 500 kg bomb penetrated the unarmoured portion of the flight deck, causing damage that required her to withdraw for repairs, although she was able to steam at 28.5 knots less than two hours after the hits. She sailed to the U.S., where repairs were completed in February 1943, after which she immediately returned to the Mediterranean. She was torpedoed by a JU-88 bomber on 15 June while supporting the build up for the invasion of Sicily (Operation Husky), and returned again to the U.S. where repairs were completed by February 1944.

Indomitable returned to the Eastern Fleet in early 1944. She and Victorious launched effective strikes against Sumatra in August and September. 

The following year, Indomitable joined the British Pacific Fleet. On the 4th of January 1945 she, her sister-ship Victorious and another fleet carrier Indefatigable attacked Medan. Subsequent actions were taken against Palembang and, yet again, Sumatra, later in January.

On 4 May 1945 she was hit by a Kamikaze, but her armoured flight deck saved her from serious damage. In August, with the war ending, Indomitable participated in the re-taking of Hong Kong. Her aircraft flew the carrier's last combat missions of the war and of her career on 31 August and 1 September against Japanese suicide boats which were attacking British forces. She returned to the UK in November 1945. The following year she carried the GB Rugby League team to Australia on their first post-war tour. In 1947, she was placed in reserve, and then given a refit that took three years, from 1947 to 1950.  Upon the completion of her refit she returned to operational duty with the Home Fleet. She was at  Elizabeth II's Coronation Review before returning to the reserve fleet. In October 1953 she was placed in unmaintained reserve. She was sold for scrap in 1955.