James B. Hartle is Research Professor and Professor of Physics Emeritus at the University of California, Santa Barbara. His scientific work is concerned with the application of Einstein's relativistic theory of gravitation --- general relativity --- to realistic astrophysical situations, especially cosmology. He has contributed usefully to the understanding of gravitational waves, relativistic stars, black holes, and the theory of the wave function of the universe. He is currently interested in the earliest moments of the big bang where the subjects of quantum mechanics, quantum gravity, and cosmology overlap. Much of his recent work is concerned with the generalizations of usual quantum mechanics that are necessary for cosmology and quantum gravity. He is a member of the US National Academy of Sciences, a fellow of the American Academy of Arts and Sciences, and is a founder and past director of the Institute for Theoretical Physics at Santa Barbara.