Frank Thomson (1841–1899) was a railroad executive from the United States, and the sixth president of the Pennsylvania Railroad (PRR).
Frank Thomson was born in Chambersburg, Pennsylvania on July 5, 1841, the son of Judge Alexander Thomson. At age 17, Thomson became an apprentice in the PRR machine shops in Altoona, and studied mechanical engineering there for four years. Thomson gained experience with restoring shops, repair of rolling stock and machinery, the rebuilding of bridges and the construction of new roads and telegraph lines. Later in his life, the press often commented he could both build a locomotive and act as its engineer.
He enlisted in the Union Army in 1861 during the American Civil War, and served as chief assistant to Colonel Thomas A. Scott, later the PRR's fourth president. As assistant to Scott, Thomson built railroads and bridges as well as directed the transport of troops and supplies. Thomson was relieved of military duty i