Five ships of the Royal Navy have borne the name HMS Cynthia. A sixth was planned but never completed:
was an 18-gun sloop launched in 1796 and broken up in 1809. was a 16-gun sloop listed between 1810 and 1815. HMS Cynthia (1826) was the Falmouth, Cornwall Post Office Packet Service packet brig , launched in 1821, that the Navy purchased in 1826, and renamed when it took over the packet service. She was wrecked off Barbados on 6 June 1827. HMS Cynthia was to have been a wooden screw sloop. She was laid down in 1861 but cancelled in 1863. was a destroyer launched in 1898, classified as a destroyer in 1913 and sold in 1920. was a launched in 1943 and transferred to the Royal Navy under lend-lease. She was returned to the US Navy in 1947.