HMS Leviathan was a 74-gun third-rate ship of the line of the British Royal Navy, launched on 9 October 1790.

[1] At the Battle of Trafalgar under Henry William Bayntun, she was near the front of the windward column led by Admiral Lord Nelson aboard his flagship, HMS Victory, and captured the Spanish ship San Agustín.

A flag said to have been flown by the Leviathan at Trafalgar is to be sold at auction by Arthur Cory in March 2016 - Bayntun is thought to have given it to his friend the Duke of Clarence (later William IV), who then gave it to Arthur Cory's direct ancestor Nicholas Cory, a senior officer on William's royal yacht HMS Royal Sovereign, in thanks for helping the yacht win a race and a bet.

[2][3] Leviathan, Pompee, Anson, Melpomene, and Childers shared in the proceeds of the capture on 10 September 1797 of the Tordenskiold.

[5] On 27 June 1812, Leviathan, Imperieuse, Curacoa and Eclair attacked an 18-strong French convoy at Laigueglia and Alassio in Liguria, northern Italy.