HMS Thetis was an Apollo-class 2nd class protected cruiser of the Royal Navy, launched on 13 December 1890. Her first significant mission was service in the Bering Sea Patrol with American warships in a combined effort to suppress poaching in the Bering Sea. The latter half of her career was spent as a mine-layer. Laden with concrete, she was deliberately sunk as a blockship in attempt to block the canal in the Zeebrugge Raid during the First World War, on 23 April 1918.