HMS Lancaster was one of 10 Monmouth-class 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 class.

The engines produced a total of 22,000 indicated horsepower (16,000 kW) which was designed to give the ships a maximum speed of 23 knots (43 km/h; 26 mph).

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

The following year Lancaster was recommissioned and assigned to the 4th Cruiser Squadron on the North America and West Indies Station.

[9][10] After the beginning of World War I in August 1914, she searched for German commerce raiders and protected convoys[11] until she returned home to join the 7th Cruiser Squadron of the Grand Fleet in 1915.