HMS Monmouth was the name ship of her class of 10 armoured cruisers built for the Royal Navy in the first decade of the 20th century.

The Monmouths were intended to protect British merchant shipping from fast cruisers like the French Guichen, Châteaurenault or the Dupleix classes.

[2] The Monmouth-class ships' main armament consisted of fourteen breech-loading (BL) 6-inch (152 mm) Mk VII guns.

[5] Monmouth, named for the Welsh county,[6] was laid down by London and Glasgow Shipbuilding at their shipyard in Govan on 29 August 1899,[1] and launched on 13 November 1901.

[8] She arrived at Devonport in late August that year for trials, but was not finally completed and accepted until 2 December 1903,[1] when she was initially assigned to the 1st Cruiser Squadron of the Channel Fleet.

[13] Post mobilisation, she was sent to the 5th Cruiser Squadron of Rear Admiral Archibald Stoddart on the Cape Verde – Canary Islands station.

[14] At the end of September, Cradock made his first fruitless search of the Tierra del Fuego area and later detached Monmouth and two other ships to search up the Chilean coast, reaching Valparaiso on 15 October, while his flagship, Good Hope returned to Port Stanley, in the Falkland Islands, to recoal and to reestablish communications with the Admiralty.

He received word on 7 October that German Vice Admiral Spee's ships were definitely bound for the Cape Horn region and waited for the elderly predreadnought battleship Canopus to reinforce his squadron.

Good Hope sailed on 22 October without her, going around Cape Horn, while Canopus and three colliers departed the following day, taking the shorter route through the Strait of Magellan.

[15] Good Hope rendezvoused with the rest of the squadron at Vallenar Roads, in the remote Chonos Archipelago of Chile on 27 October 1914 to recoal.

He sent the light cruiser Glasgow to scout ahead and to enter Coronel, Chile to pick up any messages from the Admiralty and acquire intelligence regarding German activities.

His ships were faster than the British, slowed by the 16-knot maximum speed of the armed merchant cruiser Otranto, and he opened up the range to 18,000 yards (16,000 m) until conditions changed to suit him.

The German shooting was very accurate, with both armoured cruisers quickly scoring hits on their British counterparts while still outside six-inch gun range, starting fires on both ships.

Glasgow broke contact with the German squadron at 20:05 and discovered Monmouth, listing and down by the bow, having extinguished her fires, 10 minutes later.

[19] The light cruiser Nürnberg had been trailing the German squadron and spotted the plume of smoke from Glasgow at 20:35, and then saw Monmouth with a 10-degree list to port shortly afterwards.