Margaret J. Geller is an American astrophysicist at the Center for Astrophysics | Harvard & Smithsonian. Her work has included pioneering maps of the nearby universe, studies of the relationship between galaxies and their environment, and the development and application of methods for measuring the distribution of matter in the universe.

The MacArthur Fellows Program, also known as the MacArthur Fellowship and colloquially called the "Genius Grant", is a prize awarded annually by the John D. and Catherine T. MacArthur Foundation to typically between 20 and 30 individuals working in any field who have shown "extraordinary originality and dedication in their creative pursuits and a marked capacity for self-direction" and are citizens or residents of the United States.