Denny Gulick (born Sidney Lewis Gulick III, July 29, 1936) is an emeritus professor of mathematics at University of Maryland, College Park.
Gulick graduated from Oberlin College, Ohio, then obtained his PhD from Yale University, with his main interest of operator theory. He is the leader of College Mathematics in Maryland, and is active in statewide college education and policies.
He has written several textbooks, including Encounters with Chaos (1992) and six editions of Calculus with Analytic Geometry, with fellow University of Maryland math professor Robert Ellis.