Richard Salisbury Ellis CBE FRS (born 25 May 1950, Colwyn Bay, Wales) is the Steele Professor of Astronomy at the California Institute of Technology (Caltech).
He read astronomy at University College London and obtained a DPhil at Wolfson College at the University of Oxford in 1974. After developing a strong research effort at the University of Durham (with two years at the Royal Greenwich Observatory), he was appointed a professor in 1985. In 1993 he moved to the University of Cambridge as the Plumian Professor and became a Professorial Fellow at Magdalene College. He served as Director of the Institute of Astronomy from 1994 to 1999 at which point he moved to Caltech.
Ellis works primarily in observational cosmology, considering the origin and evolution of galaxies, the evolution of large scale structure in the universe, and the nature and distribution of dark matter. Particular interests include applications using gravitational lensing and high-redshift supernovae. His most recent discoveries relate to searches for the earliest known galaxies, seen when the Universe was only a few percent of its present age.