HMS Arethusa was the name ship of the Arethusa class of light cruisers. She was laid down at Chatham Dockyard in October 1912, launched on 25 October 1913, and commissioned in August 1914 as flotilla leader for the Harwich Force.
She went on to see a considerable amount of action during the First World War. On 28 August 1914 she fought at the Battle of Heligoland Bight, flying the flag of Commodore Reginald Tyrwhitt. She was seriously damaged by the German cruisers SMS Frauenlob and SMS Stettin and had to be towed home. On 25 December of that year, Arethusa took part in the Cuxhaven Raid and on 24 January 1915 she fought at the Battle of Dogger Bank (1915). Later in the same year she was transferred to the 5th Light Cruiser squadron of the Harwich force. In September 1915 she captured four German trawlers.
On 11 February 1916 she struck a mine off Felixstowe claimed to have been laid by UC-7, drifted ashore before she could be rescued and broke her back.