HMS Cordelia was a C-class light cruiser built for the Royal Navy during World War I. She was one of six ships of the Caroline sub-class and was completed at the beginning of 1915. The ship was assigned to the 1st and 4th Light Cruiser Squadrons (LCS) of the Grand Fleet for the entire war and played a minor role in the Battle of Jutland in mid-1916. Cordelia spent most of her time on uneventful patrols of the North Sea. She spent most of 1919 as a training ship before she was recommissioned for service with the Atlantic Fleet in 1920. The ship was placed in reserve at the end of 1922 and was sold for scrap in mid-1923.
The C-class cruisers were intended to escort the fleet and defend it against enemy destroyers attempting to close within torpedo range. Ordered in July–August 1913 as part of the 1913–14 Naval Programme, the Carolines were enlarged and improved versions of the preceding Arethusa-class cruisers. The ships were 446 feet (135.9 m) long overall, with a beam of 41 feet 6 inches (12.6 m) and a mean draught of 16 feet (4.9 m). Displacement was 4,219 long tons (4,287 t) at normal and 4,733 long tons (4,809 t) at deep load. Cordelia was powered by four direct-drive Brown-Curtis steam turbines, each driving one propeller shaft, which produced a total of 40,000 indicated horsepower (30,000 kW). The turbines used steam generated by eight Yarrow boilers which gave her a speed of 28.5 knots (52.8 km/h; 32.8 mph). She carried 916 long tons (931 t) tons of fuel oil. The ship had a crew of 301 officers and other ranks.
Cordelia's main armament consisted of two BL 6-inch (152 mm) Mk XII guns that were mounted on the centreline in the stern, with one gun superfiring over the rearmost gun. Her secondary armament consisted of eight QF 4 in (102 mm) Mk IV guns, four on each side, one pair forward of the bridge, another pair abaft it on the forecastle deck and the other two pairs one deck lower amidships. For anti-aircraft defence, she was fitted with one QF 6-pounder 2.2 in (57 mm) Hotchkiss gun. The ship also mounted two twin, above-water, mounts for 21 in (533 mm) torpedoes, one on each broadside. The Carolines were protected by a waterline belt amidships that ranged in thickness from 1–3 inches (25–76 mm) and a 1-inch (25 mm) deck. The walls of their conning tower were 6 inches thick.
In August 1915, her 6-pounder anti-aircraft (AA) gun was replaced by a Ordnance QF 3-pounder 1.9 in (47 mm) Vickers Mk II anti-aircraft (AA) gun. In September–October 1917 the ship's armament was extensively revised. Her forward pair of 4-inch guns were replaced by another 6-inch gun, her aftmost 4-inch guns were replaced by another pair of 21-inch torpedo mounts and a QF 4-inch Mk V gun replaced her 3-pounder AA gun. In addition, her pole foremast was replaced by a tripod mast that was fitted with a gunnery director, her conning tower was replaced by a lighter one with thinner armour (0.75 inches (19 mm)) and a flying-off platform installed over the forecastle. This was removed between April and August 1918 when an additional 6-inch gun was added abaft the funnels in lieu of her forward main-deck 4-inch guns. Cordelia's last 4-inch guns, including the Mk V AA gun, were replaced by a pair of QF 3 in (76 mm) 20-cwt AA guns abaft the bridge, where the 4-inch guns had originally been located. Sometime between 1919 and 1923, the ship received a pair of 2-pounder 1.6 in (40 mm) Mk II "pom-pom" guns on single mounts. All of these changes adversely affected the ship's stability and the additional 21-inch torpedo tubes and the aft control position were removed by the end of 1921.
Cordelia, the third ship of her name in the Royal Navy, was laid down by Pembroke Dockyard in Pembroke Dock, Wales, on 21 July 1913. She was launched on 23 February 1914, and completed in January 1915. Commissioned into service in the Royal Navy that same month, Cordelia was assigned to the 1st Light Cruiser Squadron (LCS) of the Grand Fleet.
In early August 1914, Cordelia and the rest of her squadron were among the ships dispatched to hunt for the German commerce raider SMS Meteor, which was trying to return to Germany. Although the squadron did not find her, the German ship was forced to scuttle herself by other British cruisers on 9 August to avoid being captured.
During the Battle of Jutland on 31 May-1 June 1916, the 1st LCS was assigned to screen Vice-Admiral David Beatty's battlecruisers and were the first British ships to spot and engage the ships of the German High Seas Fleet on the afternoon of 31 May. Cordelia fired four rounds from her main armament at the light cruiser Elbing, but they fell short of the target. The ship was not heavily engaged during the battle and only fired a total of a dozen rounds from her 6-inch (152-mm) guns and three from her 4-inch (102-mm) guns. So far as is known, she did not hit anything, nor was she damaged herself. By October 1917, she had been transferred to the 4th Light Cruiser Squadron.
Cordelia remained with the 4th LCS through at least 1 February 1919. Later that month, she was reduced to reserve at Devonport. By 1 May 1919, however, she had been assigned to the Devonport Gunnery School, and by 18 January 1920 she had recommissioned for service in the 2nd Light Cruiser Squadron in the Atlantic Fleet. and remained there through 18 December 1920.
In 1921, Cordelia joined the light cruisers Caledon, Castor, and Curacoa and the destroyers Vanquisher, Vectis, Venetia, Viceroy, Violent, Viscount, Winchelsea, and Wolfhound in a Baltic cruise, departing the United Kingdom on 31 August. The ships crossed the North Sea and transited the Kaiser Wilhelm Canal to enter the Baltic Sea, where they called at Danzig in the Free City of Danzig; Memel in the Klaipėda Region; Liepāja and Riga Latvia; Tallinn, Estonia; Helsinki, Finland; Stockholm, Sweden; Copenhagen, Denmark; Gothenburg, Sweden; and Kristiania, Norway, before crossing the North Sea and ending the voyage at Port Edgar, Scotland, on 15 October 1921.
Cordelia patrolled off the coast of Ireland in 1922 during the Irish Civil War. In December 1922, she was decommissioned and placed in the Nore Reserve. She was sold for scrap in July 1923.