Jeremiah P. Ostriker has been an influential researcher in one of the most exciting areas of modern science, theoretical astrophysics, with primary work in the area of the interstellar medium, galaxies, quasars and cosmology, particularly the aspects that can be approached best by large-scale numerical calculations. He has also played a significant role in formulating and administering scientific projects and policy. He served for six years as Provost of Princeton University and is now serving a second term as Treasurer of the National Academy of Science. Dr. Ostriker, with P.J.E. Peebles, was among the first to show the importance and prevalence of dark matter in the universe and, with Paul Steinhardt, among the first to propose the current model for cosmology in which dark energy has caused the late time acceleration of cosmological expansion. Working with J.E. Gunn and D.G. York, he helped initiate the Sloan Digital Sky Survey, which, surveying the sky with a relatively small telescope, produced an enormous and diverse set of astronomical discoveries and provided the data openly to the scientific community. He played leadership roles in several of the influential national decadal reports in astronomy that helped guide this discipline to great advances in the last half century. Dr. Ostriker is a recipient of the National Medal of Science in 2000.