HMS Canopus was an 84-gun third rate ship of the line of the British Royal Navy. She had previously served with the French Navy as the Tonnant-class Franklin, but was captured after less than a year in service by the British fleet under Rear Admiral Horatio Nelson at the Battle of the Nile in 1798. Having served for less than six months for the French from her completion in March 1798 to her capture in August that year, she would eventually serve for 89 years for the British.