Eleven ships of the Royal Navy have borne the name HMS Unicorn, after the mythological creature, the unicorn:

• English ship Unicorn (1544) was a 36-gun ship captured from Scotland in 1544 and sold in 1555.
• English ship Unicorn (1634) was a 56-gun ship launched in 1634 and sold in 1687.
• HMS Unicorn (1665) (or Little Unicorn) was an 18-gun fire ship originally in Dutch service as the Eenhoorn. She was captured in 1665 and expended on 4 June 1666, on the fourth day of the Four Days' Battle.^[1]
• HMS Unicorn (1666) was a 6-gun purchased in 1666 and sunk as a blockship at Chatham on 11 June 1667, together with five other vessels, in a futile attempt to block the Dutch from advancing up the River Medway.^[2]
• HMS Unicorn (1748) was a 28-gun sixth rate launched in 1748 and broken up in 1771.
• HMS Unicorn (1776) was a 20-gun post ship launched in 1776. The French frigate Andromaque captured her^[3] on 4 October 1780^[4] took her into service as La Licorne. HMS Resource recaptured her in April 1781. The Royal Navy took her back into service as Unicorn Prize; she was broken up at Deptford in 1787.
• HMS Unicorn (1782) was a 36-gun fifth rate launched in 1782. She was renamed HMS Thalia in 1783 and was broken up in 1814.
• HMS Unicorn (1794) was a 32-gun fifth rate launched in 1794 and broken up in 1815.
• HMS Unicorn (1824) is a Leda-class frigate, launched in 1824 and converted to a powder hulk in 1860. She was a Royal Naval Reserve drill ship from 1873. She was renamed Unicorn II in 1939 and Cressy from 1941 until 1959. She was handed over to a preservation society in 1968 and is preserved in Dundee as a museum ship.
• HMS Unicorn (I72) was an aircraft maintenance carrier, launched in 1941 and broken up around 1960.
• HMS Unicorn (S43) was an Upholder-class submarine launched in 1992. She was sold to Canada in 2001, who renamed her HMCS Windsor.

Ships named Unicorn have earned the following battle honours:

• HMCS Unicorn, a Canadian Forces Naval Reserve division in Saskatoon, Saskatchewan
• French ship Licorne, similarly named ships in the French Navy
• Unicorn (Tintin), a fictional ship of the French Royal Navy featured in The Adventures of Tintin.

• Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
• Hepper, David J. (1994). British Warship Losses in the Age of Sail, 1650-1859. Rotherfield: Jean Boudriot. ISBN 0-948864-30-3.
• Roche, Jean-Michel (2005). Dictionnaire des bâtiments de la flotte de guerre française de Colbert à nos jours. Vol. 1. Group Retozel-Maury Millau. ISBN 978-2-9525917-0-6. OCLC 165892922.