HMS Earnest was launched at Leith in 1805 as one of 48 later Archer-class gun brigs for the British Royal Navy.

Earnest shared with Active, Griper, Carrier, Mariner, and Minx in the proceeds from the recapture of Francis, Tucker, master, and Betsey on 14 and 15 September.

[3] Earnest was part of the Boulogne flotilla with Cruizer, Minx, Mariner, and Griper, and so all shared in the proceeds of the recapture on 29 September of Rover, of Newcastle, Hillary, master.

[10] On 28 July Lloyd's List reported that Earnest had recaptured Vriendschap, Kok, master, which had been sailing to the Baltic when a Danish lugger had captured her.

[18] Then on 7 July Earnest captured the French privateer lugger Sacripan, of five guns and 28 men.

[19][20] Lloyd's List reported on 10 September that Primus, with tar and hemp, Worksam, in ballast, Scaleigh, with corn, Experiment, with iron, Columbus.

The "Principal Officers and Commissioners of His Majesty's Navy" announced that on 18 April they would offer for sale a number of vessels, one of them being "Earnest gun-brig, of 182 tons", lying at Deptford.

Lloyd's List reported on 1 January 1820 that as she was sailing from Pernambuco to Le Havre she ran aground near Cherbourg.

[25] On 3 December 1825 Earnest, Spooner, master, was reported to be in Memel harbour in a critical state as there was floating ice and strong currents.