HMS Indefatigable was one of the Ardent class 64-gun third-rate ships-of-the-line designed by Sir Thomas Slade in 1761 for the Royal Navy. She was built as a ship-of-the-line, but most of her active service took place after her conversion to a 44-gun razee frigate. She had a long career under several distinguished commanders, serving throughout the French Revolutionary Wars and the Napoleonic Wars. She took some 27 prizes, alone or in company, and the Admiralty authorised the issue of four clasps to the Naval General Service Medal in 1847 to any surviving members of her crews from the respective actions. She was broken up in 1816.