HMS Britannia was a 100-gun first-rate ship of the line of the Royal Navy. She was ordered on 25 April 1751 from Portsmouth Dockyard to the draught specified in the 1745 Establishment. Her keel was laid down on 1 July 1751 and she was launched on 19 October 1762. The cost of building and fitting totalled £45,844/2s/8d. Her main gundeck armament of twenty-eight 42-pounder guns was later replaced by 32-pounders. In the 1790s ten of her quarterdeck guns and two of her forecastle guns were replaced by the same number of 32-pounder carronades.