HMS Diadem was a Dido class light cruiser of the Bellona subgroup.

 She was a modified Dido design with only four turrets but improved AA armament - aka Dido Group 2. She was built on the Tyne with the keel being laid down on 15

 December 1939. She was launched on 21 August 1942, and commissioned 6 January 1944.

Diadem served on the Arctic convoys and raids against the Tirpitz in the early months of 1944, then became part of Force G off Juno Beach during the invasion of Normandy. After the landings she carried out offensive patrols against German shipping around the Brittany coast. She returned to northern waters in September, where she covered Russian convoys and carrier raids against German shipping routes along the Norwegian coast, as well as making offensive sweeps herself.

 Diadem remained with the 10th Cruiser Squadron until after the war, and served in the Home Fleet until 1950. She was placed in reserve between 1950 and 1956.

She was sold to Pakistan on 29 February 1956.