Carl Sheldon "Cap" Williams (May 16, 1872 – November 8, 1960) was an American football player, coach, and ophthalmologist. He played college football at Oberlin College and the University of Pennsylvania during the 1890s. He returned to Penn and served as the head football coach there from 1902 to 1907, compiling a record of 60–10–4. His Penn Quakers teams of 1904 and 1907 have been recognized as national champions. Williams later practiced ophthalmology for many years in Philadelphia.