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.

Pre-dreadnought battleships were sea-going battleships built from the mid- to late- 1880s to the early 1900s. Their designs were conceived before the appearance of HMS Dreadnought in 1906 and their classification as "pre-dreadnought" is retrospectively applied. In their day, they were simply known as "battleships" or else more rank-specific terms such as "first-class battleship" and so forth. The pre-dreadnought battleships were the pre-eminent warships of their time and replaced the ironclad battleships of the 1870s and 1880s.