HMS Orion was a 74-gun third rate ship of the line of the British Royal Navy, launched at Deptford on 1 June 1787 to the design of the Canada-class, by William Bately. She took part in all the major actions of the French Revolutionary and Napoleonic Wars under a series of distinguished captains.
In 1794 she fought at the Glorious First of June under Captain John Thomas Duckworth.
In early 1795, Captain James Saumarez was appointed in command. Under Saumarez, Orion took part in the defeat of the French fleet at the Battle of Groix off Lorient on 22 June.
In early 1797 she was sent to join the Mediterranean Fleet and distinguished herself at the Battle of Cape St. Vincent on 14 February. She then took part in the blockade of Cadiz from March 1797 to April 1798, when she was sent into the Mediterranean as part of a small squadron under the command of Rear-Admiral Horatio Nelson. In August, Nelson finally caught up with the French fleet, resulting in the Battle of the Nile, where Captain Saumarez was wounded.
Between 31 March 1801 and 10 July 1802 the Surgeon's First Mate on board the Orion was Henry Plowman. On 15 January 1802 whilst still on board the Orion (which was anchored at Spithead and under the command of R Cuthbert) Henry Plowman wrote his will which is signed by the Captain.
In October 1805, now under Captain Edward Codrington, she took part in the Battle of Trafalgar where, with Ajax, she forced the surrender of the French 74-gun ship Intrépide.
After Trafalgar, Orion continued in the blockade of Cadiz. On 25 November, Thunderer detained the Ragusan ship Nemesis, which was sailing from Isle de France to Leghorn, Italy, with a cargo of spice, indigo dye, and other goods. Orion shared the prize money with ten other British warships.