Girish S. Agarwal, Fellow of the Royal Society UK, (born 7 July 1946) is a theoretical physicist. He is currently at the Texas A & M University with affiliations to the Departments of Biological and Agricultural Engineering, Physics and Astronomy, and the Institute for Quantum Science and Engineering. Earlier he worked as Noble Foundation Chair and the Regents Professor at the Oklahoma State University. He is a recognized leader in the field of quantum optics and also has made major contributions to the fields of nonlinear optics, nanophotonics and plasmonics. In 2013 he published the textbook "Quantum Optics", covering a wide range of recent developments in the field, which has been well received by the community.