HMS Cardiff was a C-class light cruiser built for the Royal Navy during World War I.

The C-class cruisers were intended to escort the fleet and defend it against enemy destroyers attempting to close within torpedo range.

[4] The main armament of the Ceres-class ships consisted of five BL 6-inch (152 mm) Mk XII guns that were mounted on the centreline.

[8] Based at Scapa Flow and Rosyth during 1918, the ship spent the remainder of the war escorting convoys and training in the northern portion of the North Sea.

[9] By 21 November 1918 the war was over, and Cardiff had the honour of leading the German High Seas Fleet to the Firth of Forth to be interned.

[9] By 30 January 1920, the ship was in Constantinople and Cardiff arrived at Odessa on 4 February and Admiral Hope concurred in the decision to evacuate the city in the face of the advancing Bolsheviks.

The ship was present during the Great Fire of Smyrna almost a year later in mid-September 1922, close to the end of the Greco-Turkish War of 1919–1922.

[17] During Cardiff's time in the Mediterranean, she was fitted with a pair of 2-pounder (40 mm) Mk II "pom-pom" AA guns in 1923–24 and her original 9-foot (2.7 m) rangefinders was exchanged for 12-foot (3.7 m) models during the mid-1920s.

The ship returned home that month and replaced her half-sister Cambrian as flagship of the Nore Reserve in July.

The following year, she was transferred to the Chatham Reserve as their flagship and participated in the Silver Jubilee Fleet review for King George V on 16 July 1935.

[17] On the first day of the war on 3 September 1939, Cardiff was assigned to the 12th Cruiser Squadron which was fruitlessly searching for returning German merchant ships in the North and Norwegian Seas.

In late November, she fruitlessly searched for the German battleships Gneisenau and Scharnhorst after they sank the armed merchant cruiser, Rawalpindi, on the 23rd.

[20] Cardiff was converted for use as a gunnery training ship in October[7] and served in that capacity for the rest of the war.