HMS Otter was a Royal Navy 16-gun Merlin-class ship sloop, launched in 1805 at Hull. She participated in two notable actions in the Indian Ocean and was sold in 1828.
When built, Otter mounted sixteen 32-pounder carronades and two 6-pounder long guns. Under the rating system of the time, she was officially rated at "16 guns". From 1815 she was re-rated to "18 guns", but continued to carry the same armament.
Otter entered service in 1805 under Commander John Davies and was attached to the Channel Fleet. On 31 January 1807 Otter recaptured the Enterprize. Twenty days later, Otter recaptured the Farely.
She sailed for the Cape of Good Hope on 18 August 1807. From there Otter sailed to Montevideo to support the British attack on the Spanish colony. On arrival it was discovered that the British army had been defeated and surrendered. Davies then sailed to the Cape of Good Hope, where Commander Nesbit Willoughby took command of Otter. On 15 July 1808 Nereide, Otter, and Charwell shared in the capture of the French brig Lucie, and her cargo of slaves. Some months later, on 7 November, Leopard and Otter captured some slaves, for which they received bounty-money from the Honourable East India Company.
Otter was then attached to the squadron under Commodore Josias Rowley that was ordered to blockade the French colonies of Île Bonaparte and Île de France in the Indian Ocean. Otter raided anchorages on the islands. For instance, on 14 August 1809 her boats were in action at Riviere Noire, Île de France. Between 20 and 24 September she took part in the Raid on Saint Paul. Willoughby led the naval landing party that captured the harbour, for which he was promoted. Otter suffered one man killed and one man wounded.
After Willoughby's promotion, command initially passed to Lieutenant Edward Benge (acting). Command then passed to Commander James Tompkinson who remained in command throughout the campaign.
On 10 January 1810, Otter and Raisonable captured the Charles. Then on 30 March Otter captured two vessels, the Amazon and Gagne Petit. On 22 August Otter, Boadicea and Staunch shared in the capture of the Garronne. On 4 September the same three vessels shared in the capture of the Ranger.
More importantly, Otter operated in a supporting role in the Action of 13 September 1810 and the Action of 18 September 1810, providing towlines to the battered British frigates Africaine and Ceylon. Tompkinson was promoted into Ceylon and command passed to Lieutenant Cator during the Invasion of Île de France in December 1810. Lieutenant Thomas Lamb Polden Laugharne (acting), immediately replaced Cator and then sailed Otter back to Britain with despatches of the campaign.
Nearly four decades later her service in the battle was among the actions recognised by the clasp "Otter 18 Sept. 1810" to the Naval General Service Medal, awarded upon application to all British participants still living in 1847.
Otter was fitted for ordinary at Plymouth in April 1811. She remained in ordinary at Plymouth through 1812 to 1813 and was then was fitted for quarantine serviceas a lazaretto for Pembroke between February and April 1814. The "Principal Officers and Commissioners of His Majesty's Navy" offered the "Otter sloop, of 365 tons", lying at Pembroke, for sale on 28 March 1828. She was sold to J. Holmes for £610.