William F. Monaghan (fl. c. 1902 - 1904) was a cartographer and real estate investor involved with the power company United Electric Light and Power in New York City in the early 20th century. The details of his life are difficult to determine since there was more than one William F. Monaghan in the New York City area at the time and none of them was listed as a cartographer, civil engineer, or practitioner of a related field. Of the few traces available of his work are references to his association with United Electric, based in an office at 55 Duane St.