Illustrious-class aircraft carrier

HMS Illustrious in 1954
Class overview
Builders	Vickers-Armstrongs (3), Harland & Wolff (1)
Operators	Royal Navy
Preceded by	HMS Ark Royal
Succeeded by	Implacable class
Subclasses	HMS Indomitable
In commission	1940–1968
Planned	6
Completed	4
Scrapped	4
General characteristics (Illustrious, as built)
Type	Aircraft carrier
Displacement	23,000 long tons (23,000 t) (standard)
Length	740 ft (225.6 m) (o/a) 710 ft (216.4 m) (waterline)
Beam	95 ft 9 in (29.2 m)
Draught	28 ft 10 in (8.8 m) (deep load)
Installed power	6 Admiralty 3-drum boilers 111,000 shp (83,000 kW)
Propulsion	3 shafts; 3 geared steam turbines
Speed	30.5 knots (56.5 km/h; 35.1 mph)
Range	10,700 nmi (19,800 km; 12,300 mi) at 10 knots (19 km/h; 12 mph)
Complement	1,229
Sensors and processing systems	1 × Type 79 early-warning radar
Armament	8 × twin QF 4.5-inch dual-purpose guns 6 × octuple QF 2-pdr anti-aircraft guns
Armour	Waterline belt: 4.5 in (114 mm) Flight deck: 3 in (76 mm) Bulkheads: 4.5 in (114 mm) Hangar sides: 4.5 in (114 mm) Magazines: 3–4.5 in (76–114 mm)
Aircraft carried	36–57
Aviation facilities	1 catapult

The Illustrious class was a class of aircraft carrier of the Royal Navy that included some of the most important British warships in the Second World War. They were laid down in the late 1930s as part of the rearmament of British forces in response to the emerging threats of Nazi Germany, Fascist Italy and Imperial Japan.

The Illustrious class comprised four vessels: HM Ships Illustrious, Formidable, Victorious and Indomitable. The last of these was built to a modified design with a second, half-length, hangar deck below the main hangar deck. Each of these ships played a prominent part in the battles of the Second World War. Victorious took part in the pursuit of the German battleship Bismarck, Illustrious and Formidable played prominent parts in the battles in the Mediterranean during 1940 and 1941 and all three took part in the large actions of the British Pacific Fleet in 1945.

The later two ships of the Implacable class were also built to modified designs to carry larger air wings. Implacable and Indefatigable both had two hangar levels, albeit with a limited 14-foot (4.3 m) head room.