Richard Keith Ellis, FRS (born 17 November 1949) is a British theoretical physicist, working at the University of Durham, and a leading authority on perturbative quantum chromodynamics and collider phenomenology.

He has held positions at Imperial College, MIT, Caltech, CERN and the University of Rome.

Together with Douglas Ross and Tony Terrano he performed the first calculation of jet structure in e+e- annihilation which allowed precise determination of the strong coupling.

[6] Ellis is the coauthor with W. J. Stirling and B. R. Webber of a book on QCD and collider physics published by Cambridge University Press in 1996.

Also in 2009, Ellis together with John Collins and Davison Soper won the J. J. Sakurai Prize for Theoretical Particle Physics, For work in perturbative Quantum Chromodynamics, including applications to problems pivotal to the interpretation of high energy particle collisions.