HMS Monmouth was an Intrepid-class 64-gun third rate ship of the line of the Royal Navy, built by Israel Pownoll and launched on 18 April 1772 at Plymouth. Being relatively compact in relation to her gun power, she was affectionately known as the "Little Black Ship".

The Intrepid-class ships of the line were a class of fifteen 64-gun third rates, designed for the Royal Navy by Sir John Williams. His design, approved on 18 December 1765, was slightly smaller than Sir Thomas Slade's contemporary Worcester-class design of the same year, against which it was evaluated competitively. Following the prototype, four more ships were ordered in 1767–69, and a further ten between 1771 and 1779.