Phinehas Merrill (1767 - March 31, 1815) was an American educator, mathematician, surveyor and cartographer active in New Hampshire during the late 18th and early 19th century. Merrill was well known throughout New Hampshire as a surveyor. His survey work brought him to the attention of Philip Carrigain, then New Hampshire's Secretary of State. Carrigain was in the process of creating a large scale map of New Hampshire and Merrill surveying skills were essential to completing the project. Working together, Merrill and Carrigain completed numerous new surveys, check old surveys, and slowly pieced together a new monumental map of the state. The Carrigain Map of New Hampshire, as it came to be known, was completed in 1814, but not published until 1816, one year after Merrill's death. The devoted surveyor never saw his completed masterpiece.