Designed in response to the Moltke-class battlecruisers of the Imperial German Navy, the ships significantly improved on the speed, armament, and armour of the preceding Indefatigable class.

[1] Completed in 1913, Princess Royal participated in the Battle of Heligoland Bight a month after the start of World War I in August 1914.

Apart from providing distant support during the Second Battle of Heligoland Bight in 1917, the ship spent the rest of the war on uneventful patrols of the North Sea.

In September 1912, Princess Royal began her sea trials and developed 78,803 shp (58,763 kW) for a speed of 28.5 knots (52.8 km/h; 32.8 mph).

During maximum power trials in July 1913, the battlecruiser achieved 96,238 shp (71,765 kW) for a speed of 27.97 knots (51.80 km/h; 32.19 mph) while at the unusually high displacement of 29,660 long tons (30,140 t).

[11] After the Battle of Jutland revealed a vulnerability to plunging shellfire, 1 inch of additional armour, weighing approximately 100 long tons (102 t), was added to the magazine crowns and turret roofs.

The battlecruisers headed south at full speed at 11:35,[b] when the British light forces failed to disengage on schedule, as the rising tide meant that German capital ships would be able to clear the bar at the mouth of the Jade Estuary.

Before Cöln could be sunk, Beatty was distracted by the sudden appearance of the German light cruiser Ariadne directly to his front, and ordered pursuit.

[16] Princess Royal sailed from Cromarty on 28 September to rendezvous with a Canadian troop convoy bound for the United Kingdom.

Princess Royal arrived at Halifax on 21 November, then spent several days off New York City before she steamed down to the Caribbean to guard against the possibility that Graf Spee would use the Panama Canal.

At 11:02, Beatty had flags hoisted signalling "course north-east", to bring his ships back to their pursuit of Hipper, and "attack the rear of the enemy".

Rear-Admiral Sir Gordon Moore – temporarily commanding the squadron from New Zealand – thought the signals meant to attack Blücher, which was about 8,000 yards (7,300 m) to the north-east, and ordered the four other battlecruisers away from the pursuit of Hipper's main force to engage.

This order was rescinded when it became clear that the time lost in sinking Blücher meant the rest of Hipper's battlecruisers would reach friendly waters before they could be caught.

She also fired two 13.5-inch shrapnel shells at the German airship L 5 as its crew attempted to bomb the sinking Blücher, mistaking it for a British ship,[23] despite the fact that the maximum elevation of those guns was only 20°.

At 15:32, Beatty ordered a course change to east south-east, positioning the British ships to cut off the Germans' line of retreat, and signalled action stations.

Hipper ordered his ships to turn to starboard, away from the British, to assume a south-easterly course, and reduced speed to 18 knots (33 km/h; 21 mph) to allow three light cruisers of the 2nd Scouting Group to catch up.

[26] This began what was to be called the "Run to the South" as Beatty changed course to steer east south-east at 15:45, now paralleling Hipper's course less than 18,000 yards (16,000 m) away.

[29] By this time, the distance between the British and German ships was too great for accurate fire, so Beatty altered course four points to port between 16:12 and 16:15, closing the range.

This manoeuvre exposed Lion to the fire of the German battlecruisers, and the smoke from multiple successful hits caused Derfflinger to lose sight of Princess Royal and switch targets to Queen Mary at 16:16.

[30] At 16:30, the light cruiser Southampton, scouting in front of Beatty's ships, spotted the lead elements of the High Seas Fleet charging north at top speed.

[31] The German battlecruisers made their own turn north in pursuit,[32] but Beatty's ships maintained full speed, and gradually moved out of range.

The British battlecruisers turned north, then north-east, to try to rendezvous with the main body of the Grand Fleet, and at 17:40 opened fire again on their German counterparts.

[34] About 18:22, Princess Royal was hit by two 12-inch (305 mm) shells fired by the battleship Markgraf; one of these disabled 'X' turret and the other penetrated the ship's side armour.

[35] By 18:35, Beatty was following the 3rd BCS as they were leading the Grand Fleet east-southeast, and continuing to engage Hipper's battlecruisers to their south-west.

However, the British had altered course to the south, allowing the Grand Fleet to cross Scheer's "T" and inflict damage on the leading German ships.

[42] Along with the rest of the battlecruisers, Princess Royal reached Rosyth Dockyard in Scotland on the morning of 2 June, and she immediately received temporary repairs over the next eight days.

[44] Princess Royal provided support for British light forces involved in the Second Battle of Heligoland Bight on 17 November 1917, but never came within range of any German ships.

[46] Starting in July, the Grand Fleet was affected by the 1918 flu pandemic; at one point, Princess Royal lacked sufficient healthy crewmen to sail.

[47] Following the surrender of the High Seas Fleet at the end of the war, Princess Royal and the 1st BCS made up part of the guard force at Scapa Flow.