HMS Eagle was an Audacious-class aircraft carrier of the Royal Navy, in service 1951–1972. Until the arrival of the Queen Elizabeth-class aircraft carriers in the 21st century, she and her sister Ark Royal were the two largest Royal Navy aircraft carriers ever built.

She was laid down on 24 October 1942 at Harland and Wolff shipyard in Belfast as one of four ships of the Audacious class. These were laid down during the World War II as part of the British naval buildup during that conflict. Two were cancelled at the end of hostilities, and the remaining two were suspended. Originally called Audacious, she was renamed Eagle (the fifteenth Royal Navy ship to receive this name), taking the name of the cancelled third ship of the class on 21 January 1946. She was finally launched by Princess Elizabeth on 19 March 1946.

Although Eagle was completed in October 1951 without an angled flight deck, one was added three years later. In 1952 she took part in the first large NATO naval exercise, Exercise Mainbrace.

The Audacious-class aircraft carriers were intended as a larger follow-on to the Implacable-class of aircraft carriers with armoured hangars, with the design being modified before orders being placed to accommodate larger and heavier aircraft, which led to the displacement growing from the originally planned 27,000 long tons (27,433 t) to 32,500 long tons (33,022 t) by the time the ships were ordered. Four ships were ordered, although one, Africa, was cancelled before construction began.

The first of the class, Audacious was laid down at Harland & Wolff's Belfast shipyard on 24 October 1942. Construction was slowed by the need to concentrate resources on more urgent requirements, such as the construction of landing craft, and none of the ships of the class had been launched when the end of the Second World War brought large cuts in the shipbuilding programme for the Royal Navy. The third ship of the class, Eagle, which was only 26% complete, was canceled in December 1945, with Audacious being renamed Eagle on 21 January 1946. The newly renamed Eagle was launched by Princess Elizabeth on 19 March 1946, but construction of the two carriers was slowed for three years while the Royal Navy's requirements for aircraft carriers was reviewed, it being eventually decided to complete Eagle to a similar standard to that planned in 1945, while Ark Royal would be completed to an improved design. Eagle was finally completed on 1 October 1951.

As built, Eagle was 803 feet 9 inches (244.98 m) long overall, 750 feet 0 inches (228.60 m) at the waterline and 720 feet 0 inches (219.46 m) between perpendiculars, with a beam of 112 feet 9 inches (34.37 m) and a draught of 36 feet 0 inches (10.97 m) at deep load. Displacement was 43,060 long tons (43,751 t) standard, with full load of up to 53,390 long tons (54,247 t). Eight Admiralty three-drum water-tube boilers fed steam to Parsons single-reduction geared steam turbines rated at 152,000 shaft horsepower (113,000 kW) which in turn drove four propeller shafts. This gave a speed of 31.5 knots (36.2 mph; 58.3 km/h) at deep load.

Eagle started Sea trials on 31 October 1951, with initial flying trials starting on 14 February 1952 and the ship being accepted into service on 1 March 1952. Eagle continued to work up her crew, embarking an initial air wing equipped with two squadrons of Supermarine Attacker jet fighters, two squadrons of Fairey Firefly anti-submarine aircraft and a squadron of Blackburn Firebrand attack aircraft, and in September 1952, took part in the big NATO naval exercise, Exercise Mainbrace off the coast of Norway and Denmark.

In early 1953 Eagle visited the Mediterranean, before returning to home waters when in June she took part in the Fleet Review at Spithead to celebrate the Coronation of Queen Elizabeth II. She joined the Mediterranean Fleet in February 1954, before returning to British waters in May.