Alfred Lewis Vail (September 25, 1807 – January 18, 1859) was an American machinist and inventor. Vail was central, with Samuel F. B. Morse, in developing and commercializing the telegraph between 1837 and 1844. Vail and Morse were the first two telegraph operators on Morse's first experimental line between Washington, DC, and Baltimore, and Vail took charge of building and managing several early telegraph lines between 1845 and 1848. He was also responsible for several technical innovations of Morse's system, particularly the sending key and improved recording registers and relay magnets.
Vail left the telegraph industry in 1848 because he believed that the managers of Morse's lines did not fully value his contributions. His last assignment, superintendent of the Washington and New Orleans Telegraph Company, paid him only $900 a year, leading Vail to write to Morse, "I have made up my mind to leave the Telegraph to take care of itself, since it cannot take care of me. I shall, in a few months, leave Washington for New Jersey, ... and bid adieu to the subject of the Telegraph for some more profitable business."