Ralph Whitney Mathisen is an American ancient historian, specializing in the history of Late antiquity. Currently he is the Professor of History, Classics, and Medieval Studies at the University of Illinois Urbana-Champaign. From 1996 to 2004 he was the Louise Fry Scudder Professor of Humanities at the University of South Carolina. He also has served the founding editor of the Journal of Late Antiquity and one of the editors of Late Antiquity Newsletter, Medieval Prosopography and De Imperatoribus Romanis.