HMS Castor was one of the Cambrian subclass of the of light cruisers. She saw service during the First World War and the Russian Civil War.
Construction
Design of the Cambrian subclass was based on the earlier light cruisers and , which, in turn, were based on the subclass, using the same hull as the Carolines but with two funnels and a maximum armor thickness of as opposed to in the Carolines.
Castor was built by Cammell Laird at Birkenhead, England. Laid down on 28 October 1914, she was launched on 28 July 1915 and completed in November 1915.
Service history
World War I
thumb|left|200px|Large shell hole in the side of Castor after the Battle of Jutland
Commissioned in November 1915, Castor was the flagship of Commodore (D), assigned to the 11th Destroyer Flotilla in the Grand Fleet. She fought in the Battle of Jutland, in which she was damaged by German gunfire and suffered 10 casualties.
Post-war
After the First World War, Castor served in the Black Sea from 1919 to 1920 during the British intervention in the Russian Civil War. In April 1920, she recommissioned at Chatham Dockyard for service in the 2nd Light Cruiser Squadron in the Atlantic Fleet.
Castor patrolled off the coast of Ireland in 1922 during the Irish Civil War. She was assigned to the Gunnery School at Portsmouth from 1923 to 1924, then was in the Nore Reserve from 1924 to 1925.