HMS Orestes was an 18-gun Dutch-built brig-sloop of the Royal Navy. She was originally built as the privateer Mars, which the British captured in 1781. She went on to serve during the Fourth Anglo-Dutch War and the French Revolutionary Wars.
The privateer was one of two captured in the North Sea in November 1781, both of which were taken into the Navy. Orestes became an effective anti-privateer vessel, taking several enemy vessels while serving off the British coast. She divided her time between a number of the Royal Navy's stations, serving in the West Indies and departing for the East Indies after time spent on the French coast. Her career in the Indian Ocean was short-lived, as she disappeared at sea in 1799, and is presumed to have foundered in a hurricane with the loss of her entire crew.
Dutch service
Mars was built at Amsterdam in 1781, to prey on British shipping during the Fourth Anglo-Dutch War. On 30 November she sailed from the Texel with another large privateer, the Hercules. The vessels were commanded by a father and son team, by the name of Hogeboom; the father had been active as a privateer operating out of Flushing during the Seven Years' War under the alias John Hardapple. The two vessels were estimated to have cost upwards of £20,000. Artois had one man killed and six wounded in the whole engagement.
Royal Navy service
Orestes was fitted out at Deptford between February and August 1782, with her armament consisting of 18 short nine-pounders and ten ½-pounder swivel guns. Ellis remained as captain for the next two and a half years, being succeeded by Commander Manley Dixon in June 1786.
Fate
Orestes sailed for the East Indies in August 1798, remaining on that station until disappearing in the Indian Ocean in November 1799.