Owen Brian Toon (born May 26, 1947 in Bethesda, Maryland) is a professor of atmospheric and oceanic sciences. He is a fellow at the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder. He received an A.B. in physics at the University of California, Berkeley in 1969 and a Ph.D. in physics at Cornell University in 1975 under Carl Sagan. His research interests are in cloud physics, atmospheric chemistry, and radiative transfer. He also works on comparing Earth and other planets such as Venus.