Frank Manly Thorn (December 7, 1836 – April 14, 1907) was an American lawyer, politician, government official, essayist, journalist, humorist, and inventor. He served as the sixth Superintendent of the United States Coast and Geodetic Survey. The first non-scientist to hold that position, he guided the Coast and Geodetic Survey through a critical period of reform following the exposure of improprieties under his predecessor, and he defended it from being abolished or diminished by its critics.