HMS Cormorant was probably launched in 1803 at Howden Pans as the merchant ship Blenheim.

After the Admiralty sold her in 1817, she resumed the Blenheim name and returned to mercantile service as a West Indiaman.

[1] In June Commander James Stewart commissioned Cormorant for the North Sea.

[7] Phillimore left Cormorant in October, and Commander William Hughes replaced him.

[1] However, Lloyd's List reported on 24 March 1809 that the sloop-of-war Cormorant had detained Batavia, sailing from Rochelle to New York.

[1] Disposal: The "Principal Officers and Commissioners of His Majesty's Navy" offered the "Cormorant storeship, of 328 tons", lying at Chatham, for sale on 3 April 1817.

[1] Blenheim reentered Lloyd's Register in 1818 with Souter, master, S. Moates, owner, and trade London–Honduras.

[19] A tremendous gale hit the southeast coast of England on 5 March, damaging or even wrecking many vessels.

[20] The Register of Shipping for 1823 showed Blenheim with Webster, master, S. Moats, owner, and trade Bristol–Jamaica.

[21] Lloyd's List reported on 26 March 1822 that Blenheim, "late Webster", master, had departed from Annato Bay, Jamaica, on 10 November 1821 for London.