Lord Eldon, variously described as an "armed defense ship", a "hired armed ship", or simply "armed ship", was a 16-gun hired armed vessel serving the Royal Navy. The first mention of her in readily available sources is on 29 October 1804. The London Star reported that "also arrived the hired armed ship Lord Eldon, from a cruise".
Then on 12 November 1804 Lord Eldon was under the command of Commander Francis Newcombe when eight or ten gunboats captured her off Algeciras. However, two days later HMS Eurydice and HMS Bittern recaptured her and sent her into Gibraltar. Her master and seven sailors had been wounded.
In February 1806 Newcombe took command of HMS Beagle. His replacement on Lord Eldon was Commander G.B. Whinyates.
In 1807 Commander John Bradley took command of Lord Eldon on the coast of Spain. His replacement at the end of the year was Commander G.B. Whinyates.
On 28 November 1808 HMS Delight, HMS Active (1799), the supply ship HMS Woolwich, and Lord Eldon escorted a convoy of 50 vessels out of Malta, bound for Gibraltar, Lisbon, and London. However, contrary winds forced about 40 merchantmen, and the escorts to return to Malta within two weeks. In 1808/09 Lord Eldon was under the command of Commander C.C. Fisher.
There is no information readily available online that mentions when the Navy returned Lord Eldon to her owners or her subsequent fate.