HMS Yarmouth was a 64-gun third rate ship of the line of the Royal Navy, built at Deptford Dockyard. She was previously ordered to the dimensions specified in the 1741 proposals for modifications to the 1719 Establishment, but the Admiralty had very quickly concluded that these were too small, and as an experiment in 1742 authorised an addition of 6ft to the planned length, and the Yarmouth was re-ordered to the enlarged design in June 1742. She was built at Deptford, where the Admiralty felt they could best observe the effectiveness of the added size, and launched on 8 March 1745.