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.

[4] In 1914 the shelter-deck guns were enclosed in casemates[5] and a fire-control director was installed sometime in 1914, before August, on a platform below the spotting top.

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.

[14] On 8 August, Monarch was conducting gunnery practice south-east of Fair Isle when she was unsuccessfully attacked by a submarine-fired torpedo.

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.

On the evening of 22 November 1914, the Grand Fleet conducted a fruitless sweep in the southern half of the North Sea; Monarch stood with the main body in support of Vice-Admiral David Beatty's 1st Battlecruiser Squadron.

They mustered the six dreadnoughts of Vice-Admiral Sir George Warrender's 2nd BS, including Monarch and her sister ships, Orion and Conqueror, and Beatty's four battlecruisers.

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.

Almost three weeks later, Monarch 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, Monarch 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.

[26] On 31 May, Monarch, under the command of Captain George Borrett, was the sixth ship from the head of the battle line after deployment.

[27] During the first stage of the general engagement, the ship fired three salvos of armour-piercing, capped (APC) shells from her main guns at a group of five battleships at 18:32, scoring one hit on the dreadnought SMS König that knocked out a 15-centimetre (5.9 in) gun, temporarily disabled three boilers and started several small fires.

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.

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

[38] A replica of the underwater side protection of the Nelson-class battleships added to test the blast effects of large bombs detonating alongside the hull.

[39] On 20 January 1925, Monarch was towed out from Plymouth by dockyard tugs into Hurd's Deep in the English Channel, approximately 50 nautical miles (93 km; 58 mi) south of the Isles of Scilly.

On 21 January she was attacked by a wave of Royal Air Force bombers, which scored several hits; this was followed by four C-class light cruisers firing six-inch (152-mm) shells, and the destroyer Vectis, using her 4-inch guns.