HMS Iron Duke was a Battleship and the lead ship of her class.  She served as the flagship of the Grand Fleet during WWI, including at the Battle of Jutland. For the majority of the Great War, she was based with the rest of the Grand Fleet at Scapa Flow.

Iron Duke was launched on 12 October 1912 at Portsmouth. After commissioning, she joined the Home Fleet as the flagship of Admiral Sir George Callaghan. Shortly before the beginning of hostilities, Callaghan was relieved by Admiral Sir John Jellicoe, who made Iron Duke the flagship of the Grand Fleet.

Her major combat service during the First World War came in the Battle of Jutland on 31 May 1916, where she served in the 4th Battle Squadron. She delivered a number of significant shell hits on the German battleship Konig.  She later became the flagship for a short time of Admiral Sir David Beatty when he assumed command of the Grand Fleet in late 1916

After the war, she was transferred to the Mediterranean, where she again served as flagship, this time for Admiral Sir John de Robeck. She served with the Mediterranean and Atlantic Fleets until she was paid off in 1929.

During WWII she was used as a base ship at Scapa Flow, where she became an air attack target for three German bombers and was forced to beach; despite severe damage the ship was patched enough to enable her to avoid sinking. She was refloated and saw continued service until the conclusion of hostilities.  She was broken up in 1948.