In response to developments in the Baltic in 1801 that threatened to deprive Britain of much-needed naval supplies, "Agamemnon" was sent as part of a fleet under Admiral Sir Hyde Parker and Vice-Admiral Lord Nelson to attack the Danish at Copenhagen. On 2 April, "Agamemnon" was part of Nelson's division that fought the Battle of Copenhagen. "Agamemnon" was positioned second in the line after , and after passing down the Outer Channel, she grounded whilst attempting to round the southern tip of the Middle Ground shoal. While the battle raged around her "Agamemnon", along with and , both of which had also run aground, flew signals of distress. The three stranded ships were eventually pulled off the Middle Ground in the night of 3 April.