Two ships of the British Royal Navy have been named HMS Canopus :
HMS Canopus was also the name of a Royal Navy training base at Alexandria in World War II.
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.
Her career began as the flagship of Rear-Admiral Armand Blanquet du Chayla, second in command at the Battle of the Nile, where she distinguished herself with her fierce resistance before being forced to surrender with over half her crew dead or wounded, and most of her guns disabled. Taken into British service she was refitted and served as the flagship of several admirals. Commanded by Francis Austen Canopus was Rear-Admiral Thomas Louis's flagship in the Mediterranean under Nelson, and narrowly missed the fighting at Trafalgar. She saw action with Duckworth's fleet at the Battle of San Domingo, and remained with him during the attempt to force the Dardanelles, and the operations in support of the Alexandria expedition in 1807. She remained active against the French in the Mediterranean for the rest of the Napoleonic Wars, helping to drive ashore two large French ships of the line in a notable incident in 1809. Canopus remained in service after the end of the wars, serving as a flagship into the mid-nineteenth century, but as sail gave way to steam, she was relegated to support duties in Devonport, becoming a receiving ship, tender and a mooring hulk. She was eventually sold for breaking up in 1887, after nearly ninety years in British service.
HMS Canopus was a pre-dreadnought battleship of the British Royal Navy and the lead ship of the Canopus class. At the beginning of the First World War she was involved in the search for the German East Asia Squadron of Admiral Graf Spee. Too slow to follow Admiral Sir Christopher Cradock's cruisers, she missed the Battle of Coronel, but fired the first shots of the Battle of the Falklands. Transferred to the Mediterranean she took part in the Naval operations in the Dardanelles Campaign.
HMS Canopus was laid down at Portsmouth Dockyard on 4 January 1897, launched on 12 October 1897, and completed on 5 December 1899. She was named after the ancient city of Canopus, Egypt, where the Battle of the Nile took place.
Canopus and her five sister ships were designed for service in the Far East, where the new rising power Japan was beginning to build a powerful and dangerous navy. These vessels were intended to be able to transit the Suez Canal. They were designed to be smaller (by about 2,000 tons), lighter and faster than their predecessors, the Majestic-class battleships, although they were slightly longer at 430 feet (131 m). To save weight, Canopus carried less armour than the Majestics, although the change from Harvey armour in the Majestics to Krupp armour in Canopus meant that the loss in protection was not as great as it might have been, Krupp armour having greater protective value at a given weight than its Harvey equivalent. Still, the armour of the Canopus class was light enough to make them almost second-class battleships. Part of their armour scheme included the use of a special 1-inch (2.54 mm) armoured deck over the belt to defend against plunging fire by howitzers that France reportedly planned to install on its ships, although this report proved to be false.