HMS Euryalus was a Dido-class cruiser of the Royal Navy. She was laid down at Chatham Dockyard on 21 October 1937, launched on 6 June 1939, and commissioned 30 June 1941. Euryalus was the last cruiser built at the dockyard.

The Dido class consisted of sixteen light cruisers built for the Royal Navy during World War II. The first group of three ships were commissioned in 1940; the second group of six ships and third group of two were commissioned between 1941 and 1942. A fourth group, also described as the Improved Dido or Bellona class were commissioned between 1943 and 1944. Most members of the class were given names drawn from classical history and legend. The groups differed in armament, and for the Bellonas, in function. The Dido class were designed to replace the C-class and D-class cruisers as small fleet cruisers and flotilla leaders for the destroyer screen. As designed, they mounted five twin 5.25-inch high-angle gun turrets on the centreline providing dual-purpose anti-air and anti-surface capacity; the complex new turrets were unreliable when introduced, and somewhat unsatisfactory at a time when the UK faced a fight for survival. During the war, the original 1939-42 ships required extensive refit work to increase electrical generating capacity for additional wartime systems and in the final Bellona, HMS Diadem, fully-electric turrets. While some damage was experienced initially in extreme North Atlantic weather, changes to gun handling and drill partially mitigated the problems. The fitting of the three forward turrets in the double-superfiring A-B-C arrangement relied upon the heavy use of aluminium in the ships' superstructure, and the lack of aluminium after the evacuation of the British Army from France was one of the primary reasons for the first group only receiving four turrets, while the third group received four twin 4.5-inch mounts and no 5.25-inch guns at all. The Bellonas were designed from the start with four radar-directed 5.25-inch gun turrets with full Remote Power Control and an expanded light anti-aircraft battery, substantially increasing their efficiency as AA platforms.