The fourth Conqueror to serve in the Royal Navy was built in Graham's yard at Harwich to a design modified from Sir John Henslow's 'Mars' class of two-deckers dating from the previous decade. This particular Conqueror was ordered on 30th April 1795, laid down in October the same year and launched on 23rd November 1801. Measured at 1,854 tons, she was 176 feet in length (overall) with a 49 foot beam and mounted 74 guns including a main armament of 28-32pounders on her gundeck.
Serving throughout the Napoleonic Wars once hostilities resumed after the short-lived Peace of Amiens, her principal encounter with the enemy took place on 21st October 1805 when the combined Franco-Spanish fleet was destroyed at Trafalgar. Present there under the command of Captain (later Admiral Sir) Israel Pellew, Nelson placed Conqueror in the weather column where she was third-in-line behind Victory. Engaging and then accepting the surrender of the French flagship Bucentaure, she also did the same to the huge Spanish four-decker Santissima Trinidad and emerged from the battle much damaged and having lost most of her figurehead to enemy fire which was later replaced by a bust of Nelson. In November 1807, still under Pellew's command, she was sent to Lisbon to join the squadron protecting British interests and to save the Portuguese Royal Family from the invading French army, the latter being successfully accomplished before the year ended.