Named in honor of Donald E. Osterbrock (b. 1924), professor of astronomy and astrophysics at the University of Wisconsin-Madison (1958-1973) and at the University of California at Santa Cruz and UCO/Lick Observatory (1972-199 and director of the Lick Observatory (1973-1981). His research spans gaseous nebulae, interstellar matter, galactic structure, and quasars and active nuclei of galaxies, and he has authored a historical series on the life and work of several astronomers who played vital roles in the progress of American astronomy. Osterbrock served as president of the American Astronomical Society during 1987-1989. He is a member of the National Academy of Sciences and the National Academy of Arts and Sciences. Citation prepared by A.R. Klemola.