HMS Invincible was the lead ship of her class of three battlecruisers built for the Royal Navy during the first decade of the twentieth century and the first battlecruiser to be built by any country in the world. During the First World War, she participated in the Battle of Heligoland Bight in a minor role, as she was the oldest and slowest of the British battlecruisers present. During the Battle of the Falkland Islands, Invincible and her sister ship Inflexible sank the armoured cruisers Scharnhorst and Gneisenau almost without loss to themselves, despite numerous hits by the German ships.

She was the flagship of the 3rd Battlecruiser Squadron during the Battle of Jutland in 1916. The squadron had been detached from Admiral Beatty's Battlecruiser Fleet a few days before the battle for gunnery practice with the Grand Fleet and acted as its heavy scouting force during the battle. She was destroyed by a magazine explosion during the battle after the armour of one of her gun turrets was penetrated.

Invincible was significantly larger than her armoured cruiser predecessors of the Minotaur class. She had an overall length of 567 ft (173 m), a beam of 78.5 ft (23.9 m), and a draft of 30 ft (9.1 m) at deep load. She displaced 17,250 long tons (17,530 t) at load and 20,420 long tons (20,750 t) at deep load, nearly 3,000 long tons (3,000 t) more than the earlier ships.

The Invincible-class ships were formally known as armoured cruisers until 1911 when they were redesignated as battlecruisers by an Admiralty order of 24 November 1911. Unofficially a number of designations were used until then, including cruiser-battleship, dreadnought cruiser and battle-cruiser.

Invincible had two paired sets of Parsons turbines, each of which was housed in a separate engine-room and drove an outboard and inboard shaft. The high-pressure ahead and astern turbines were coupled to the outboard shafts and the low-pressure turbines to the inner shafts. A cruising turbine was also coupled to each inner shaft; these were not used often and were eventually disconnected. Her three-bladed propellers were 11 feet (3.4 m) in diameter on the inner shafts while the outer propellers were 10 feet (3.0 m) in diameter. The turbines were powered by thirty-one Yarrow water-tube boilers in four boiler rooms, and were designed to produce a total of 41,000 shaft horsepower (31,000 kW), but reached nearly 46,500 shp (34,700 kW) during trials in 1908. She was designed for 25 knots (46 km/h; 29 mph), but reached 26.64 knots (49.3 km/h; 30.7 mph) during trials.

Invincible carried 2,997 long tons (3,045 t) of coal, and an additional 738 long tons (750 t) of fuel oil that was to be sprayed on the coal to increase its burn rate. At full fuel capacity, she could steam for 3,090 nautical miles (5,720 km; 3,560 mi) at a speed of 10 knots (19 km/h; 12 mph). Her electrical power was provided by four 200 kW turbo-generators and motor generators with capacity of 100 kW.

Invincible carried eight BL 12-inch (305 mm) Mk X guns in four twin turrets. For evaluation purposes these were electrically driven BIX and BX turrets, two each built by Vickers and Armstrongs. They proved to be a failure despite two lengthy refits in 1909 and 1911 and were converted to hydraulic power during her refit in early 1914 at a cost of £151,200. The situation was so bad during her gunnery trials in October 1908 that the captain of HMS Excellent, the Royal Navy's chief gunnery school, described their operation in the following manner: "When the order was given to train the turret, elevate or run a gun in or out, it was only necessary to push a button, or move a switch, but the result was often a flash of blue flame which seemed to fill the turret."

Her secondary armament consisted of sixteen 4-inch (102 mm) QF Mk III guns. During 1915 the turret roof guns were transferred to the superstructure and the total number of guns was reduced to twelve. All of the remaining guns were enclosed in casemates and given blast shields at that time to better protect the gun crews from weather and enemy action. Her anti-aircraft armament consisted of a single QF 3 inch 20 cwt AA gun on a high-angle MkII mount at the aft end of the superstructure that was carried between October–November 1914 and from April 1915 onwards. A 3-pounder Hotchkiss gun on a high-angle MkIc mounting with a maximum elevation of 60° was also mounted in November 1914. Five 18 in (450 mm) submerged torpedo tubes were fitted on the Invincibles, two on each side and one in the stern. Fourteen torpedoes were carried for them.