HMS Agamemnon was one of two Lord Nelson-class pre-dreadnought battleships launched in 1906 and completed in 1908. She was the Royal Navy's second-to-last pre-dreadnought battleship to be built, followed by her sister ship, Lord Nelson. She was assigned to the Channel Fleet when the First World War began in 1914. The ship was transferred to the Mediterranean Sea with Lord Nelson in early 1915 to participate in the Dardanelles Campaign. She made a number of bombardments against Turkish fortifications and in support of British troops. Agamemnon remained in the Mediterranean after the conclusion of that campaign to prevent the German battlecruiser SMS Goeben and light cruiser Breslau from breaking out into the Mediterranean. Agamemnon shot down the German Zeppelin LZ-55 (LZ-85) during a bombing mission over Salonica in 1916. On 30 October 1918, the Ottoman Empire signed the Armistice of Mudros on board the ship while she was anchored at Lemnos in the northern Aegean Sea. She was converted to a radio-controlled target ship following her return to the United Kingdom in March 1919 and began service in 1921. Agamemnon was the last pre-dreadnought in service with the Royal Navy; she was replaced by Centurion at the end of 1926 and sold for scrap in January 1927.

The Lord Nelson class consisted of a pair of pre-dreadnought battleships built for the Royal Navy in the first decade of the twentieth century. Although they were the last British pre-dreadnoughts, both were completed and commissioned well over a year after HMS Dreadnought had entered service in late 1906. Lord Nelson and Agamemnon were assigned to the Home Fleet when completed in 1908, with the former ship often serving as a flagship. The sister ships were transferred to the Channel Fleet when the First World War began in August 1914. They were transferred to the Mediterranean Sea in early 1915 to participate in the Dardanelles Campaign.