Theodore Lyman (; November 23, 1874 – October 11, 1954) was a
U.S. physicist and
spectroscopist, born in
Boston. He graduated from
Harvard in 1897, from which he also received his
Ph.D. in 1900. He became an assistant professor in
physics at Harvard, where he remained, becoming full
professor in 1917, and where he was also director of the Jefferson Physical Laboratory (1908–17). Dr. Lyman made important studies in phenomena connected with
diffraction gratings, on the
wavelengths of vacuum
ultraviolet light discovered by
Victor Schumann and also on the properties of light of extremely short
wavelength, on all of which he contributed valuable papers to the literature of
physics in the proceedings of scientific societies.