The fourth HMS Ocean was a Canopus-class battleship of the British Royal Navy. Commissioned in 1900, she entered service with the Mediterranean Fleet until January 1901, when she was transferred to the China Station. She was recalled from China in 1905 for service with the Channel Fleet after a period spent in reserve. From 1908 to early 1910, she was again assigned to the Mediterranean Fleet. By now outclassed by the emergence of the dreadnoughts, she was assigned to the Home Fleet.Assigned to the 8th Battle Squadron following the outbreak of World War I, Ocean was involved in operations around Ireland. She also escorted troop convoys from India and assisted in the defence of the Suez Canal. In 1915, she was involved in the Dardanelles Campaign. On 18 March, she attempted to retrieve HMS Irresistible, which had been badly damaged by a mine in Erenkui Bay, but had to abandon her salvage efforts due to heavy Turkish gunfire. She instead evacuated the surviving crew of Irresistible but struck a mine while making for the open sea. Badly damaged, her crew and the survivors of Irresistible were taken off by destroyers and Ocean left to sink in Morto Bay.