Seven ships of the British Royal Navy have been named HMS Orion, after the hunter Orion of Greek mythology:

• HMS Orion (1787) was a 74-gun third-rate ship of the line launched in 1787 and broken up in 1814.
• HMS Orion (1854) was an 80-gun second-rate screw ship launched in 1854 and broken up in 1867.
• HMS Orion (1879) was an armoured corvette built for the Ottoman Empire but purchased by the Royal Navy in 1878 and launched in 1879. She was converted to a depot ship and renamed HMS Orontes in 1909, and was sold in 1913.
• HMS Orion was to have been an armoured cruiser. She was projected in 1904 but never built.
• HMS Orion (1910) was an Orion-class battleship launched in 1910 and sold in 1922.
• HMS Orion (85) was a Leander-class light cruiser launched in 1932 and sold in 1949.
• Orion was a French submarine seized in 1940, laid up until 1943 and then broken up.

• HSwMS Orion, two ships of the Swedish Navy
• HMAS Orion was an Oberon-class submarine of the Royal Australian Navy launched in 1974 and decommissioned and laid up in 1996.
• Orion (ship), various ships named Orion

• 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.