HMS Orion was the lead ship of her class of four dreadnought battleships built for the Royal Navy in the early 1910s.

Aside from participating in the failed attempt to intercept the German ships that had bombarded Scarborough, Hartlepool and Whitby in late 1914, the Battle of Jutland in May 1916 and the inconclusive action of 19 August, her service during World War I generally consisted of routine patrols and training in the North Sea.

The turbines were rated at 27,000 shaft horsepower (20,000 kW) and were intended to give the battleships a speed of 21 knots (39 km/h; 24 mph).

The ships carried enough coal and fuel oil to give them a range of 6,730 nautical miles (12,460 km; 7,740 mi) at a cruising speed of 10 knots (19 km/h; 12 mph).

[3] The Orion class was equipped with 10 breech-loading (BL) 13.5-inch (343 mm) Mark V guns in five hydraulically powered twin-gun turrets, all on the centreline.

[6] Two flying-off platforms were fitted aboard the ship during 1917–1918; these were mounted on 'B' and 'Q' turret roofs and extended onto the gun barrels.

[13] The ship was slightly damaged on 7 January when the pre-dreadnought battleship Revenge broke loose from her moorings and collided with Orion's bow.

[15] The three sisters were present with the 2nd BS to receive the President of France, Raymond Poincaré, at Spithead on 24 June 1913 and then participated in the annual fleet manoeuvres in August.

[18] On 8 August, Orion was towing a target for the dreadnought Ajax and Monarch when the latter reported that she had been unsuccessfully attacked by a torpedo and the gunnery exercise was terminated.

Almost two weeks later, the ship began having serious problems with her condensers and Jellicoe ordered that they be retubed while she was detached to the coaling base at Loch Ewe, on the northwest coast of Scotland.

The squadron departed for gunnery practice off the northern coast of Ireland on the morning of 27 October and the dreadnought Audacious struck a mine, laid a few days earlier by the German armed merchant cruiser SS Berlin.

The Germans got the better of the initial exchange of fire, severely damaging several British destroyers, but Admiral Friedrich von Ingenohl, commander of the High Seas Fleet, ordered his ships to turn away, concerned about the possibility of a massed attack by British destroyers in the dawn's light.

A series of miscommunications and mistakes by the British allowed Hipper's ships to avoid an engagement with Beatty's forces.

One of these occurred when Orion's lookouts spotted the light cruiser SMS Stralsund and failed to engage because Arbuthnot refused to allow the ship to open fire without a command from Warrender.

[21] Jellicoe's ships, including Orion, conducted gunnery drills on 10–13 January 1915 west of Orkney and the Shetland Islands.

Almost three weeks later, Orion participated in another fleet training operation west of Orkney during 2–5 November and repeated the exercise at the beginning of December.

On the night of 25 March, Orion and the rest of the fleet sailed from Scapa Flow to support Beatty's battlecruisers and other light forces raiding the German Zeppelin base at Tondern.

On 21 April, the Grand Fleet conducted a demonstration off Horns Reef to distract the Germans while the Imperial Russian Navy relaid its defensive minefields in the Baltic Sea.

[30] Rear-Admiral William Goodenough assumed command of the division on 5 December[13] and Captain Eric Fullerton relieved Backhouse on the 14th.

They enforced strict wireless silence during the operation, which prevented Room 40 cryptanalysts from warning the new commander of the Grand Fleet, Admiral Beatty.

The British only learned of the operation after an accident aboard the battlecruiser SMS Moltke forced her to break radio silence to inform the German commander of her condition.

[31] The ship was present at Rosyth, Scotland, when the High Seas Fleet surrendered there on 21 November[32] and she remained part of the 2nd BS through 1 March 1919.

[33] By 1 May, Orion had been assigned to the 3rd BS of the Home Fleet and was serving as the flagship for Rear-Admiral Sir Douglas Nicholson, second-in-command of the squadron.

On 19 December Orion was sold for scrap to Cox and Danks and she arrived at Upnor in February 1923 to begin demolition.