Ann and Amelia was a three-decker merchant ship launched in 1781. The British East India Company (EIC) twice employed her as an "extra ship", first when she went out to India to sail in trade in that market, and again in 1803 when she sailed back from India to Britain. On her return to Britain the Admiralty purchased her in June 1804 and converted her to a 44-gun fifth rate with the name HMS Mediator. The Navy converted her to a storeship in 1808, but then expended her as a fireship at the battle of the Basque Roads in April 1809.