HMS Agamemnon was a Royal Navy third-rate ship of the line with an armament of 64 guns. She was built at Buckler’s Hard on the Beaulieu River in the New Forest, was launched on the 10th of April 1781, and served until 1809 when she was lost after running aground on a shoal in the mouth of the River Plate.

Launched during the American War of Independence, she was immediately put into commission. Initially destined for the East Indies, she sighted a large Franco-Spanish fleet in the Channel and returned home to report the news to the Admiralty. She then joined the Channel Fleet. In December, 1781, she was part of a squadron of 12 of the line under Rear-Admiral Kempenfelt that was sent out to intercept a French fleet and convoy expected to sail from Brest for the West Indies.

Early in 1782 she was sent out to join the British fleet in the Leeward Islands, arriving in time to take part in the Battle of the Saintes.

After the end of the American War, she was laid up in ordinary (at Chatham?) until the outbreak of the French Revolutionary Wars in 1793.

In 1793, Agamemnon was recommissioned under Captain Horatio Nelson and sent out to join the Mediterranean Fleet under Lord Hood. It was during this command that Nelson lost the sight of his right eye at the siege of Calvi, Corsica, in 1794. By 1796 she was worn out and returned home in the summer -- without Nelson, by now a commodore, who shifted his broad pennant to the Captain.

In 1805 Agamemnon, by then under the command of Sir Edward Berry, took part in the Battle of Trafalgar.

In 1806 she took part in the Battle of San Domingo.

See HMS Agamemnon for other ships of this name.