HMS Piercer was a Royal Navy launched in 1804. She served against the French, Danes and Dutch in the Napoleonic Wars and was assigned to the Downs station. She participated in a number of operations in the Bay of Biscay, the English Channel, and the North Sea. In 1814 the British government transferred Piercer to the Kingdom of Hanover for use as a guard ship. Hanover decommissioned her in 1850. British service Lieutenant Thomas Carew commissioned Piercer in September 1804. The next year she came under the command of Lieutenant John Sibrell, who had just transferred from the hired armed cutter Duchess of Cumberland, and who sailed her amongst the Channel Islands. In June 1805 Lieutenant Carter assumed command, apparently temporarily. On 3 August 1805, Piercer was in a squadron with , , , , and when they captured the Frederick Wilhelm. At the time, Sibrell was in command of Piercer. Then on 8 April 1806, Basilisk captured Mercurius. Piercer shared in the prize money by private agreement. In January 1807, Sibrell sailed Piercer for the North Sea. On 15 October Piercer, and were in company at the capture of the Danish bark Narbvalen. Piercer shared by agreement in the proceeds of 's capture of the Danish ship Gamble Norge. On 15 October Piercer was in company with and at the capture of the Danish brig Narhvalen and so later shared in the proceeds. In November 1808 Sibrell captured the Danish vessels Catherina (4 November), and Speculation (6 November). In January 1809, Piercer was driven ashore on the coast of Sweden. She was refloated, repaired, and returned to service. During the Gunboat War, a flotilla of 25 Dano-Norwegian gunboats attacked a British convoy on 9 June 1809 off the island of Saltholm in Øresund Strait near Copenhagen. Piercer was one of the four British warships escorting the convoy. During the engagement the Danes captured 10 or 12 merchant vessels, as well as the gunbrig . captured two French chasse marees, the Camilla and the Bonne Rencontre, on 6 May 1810; Piercer and were in company. Piercer and the gun-brig were in company with Surveillante when on 23 June she captured the chasse marees Margaret and the Eclair. On 12 September 1810, Piercer was in company with a squadron under the command of Rear Admiral Sir H.B. Neal when captured the chasse maree Sophie. The vessels sharing in the prize included