James Edward Gunn (born 1938) is the Eugene Higgins Professor of Astronomy at Princeton University. He received the 2009 National Medal of Science.
Gunn's early theoretical work in astronomy has helped establish the current understanding of how galaxies form, and the properties of the space between galaxies. He also suggested important observational tests to confirm the presence of dark matter in galaxies, and predicted the existence of a Gunn-Peterson trough in the spectra of distant quasars.
Gunn is one of those rare astronomers who can build research-grade astronomical detectors and work in theoretical astrophysics with equal facility.