Curtis Gove Callan, Jr. (born October 11, 1942) is a theoretical physicist and a professor at Princeton University. He has conducted research in gauge theory, string theory, instantons, black holes, strong interactions, and many other topics. He was awarded the Sakurai Prize in 2000 ("For his classic formulation of the renormalization group, his contributions to instanton physics and to the theory of monopoles and strings") and the Dirac Medal in 2004.Callan received his B.Sc.