Gray is the Arnold O. Beckman Professor of Chemistry and Founding Director of the Beckman Institute at the California Institute of Technology. Gray began his work in inorganic chemistry with Fred Basolo and Ralph Pearson at Northwestern University, where he earned his Ph.D. in 1960. After a postdoctoral year with Carl Ballhausen at the University of Copenhagen, he joined the chemistry faculty at Columbia University, and moved to the California Institute of Technology in 1966.

Dr. Gray has investigated the syntheses, structures and reactions of inorganic complexes and, for over 20 years, has worked on the electronic structures and electron-transfer reactions of metalloproteins. He was elected to the National Academy of Sciences in 1971, and in 1986 received the National Medal of Science for his contributions to bioinorganic chemistry and inorganic photochemistry. In addition to twelve honorary degrees, Gray's awards include the American Institute of Chemists Gold Medal, the Pauling Medal, the Gibbs Medal, the Waterford Prize, the Bader Award, the Priestley Medal, the Linderstrom-Lang Prize, the Harvey Prize, the Benjamin Franklin Medal in Chemistry, and the Wolf Prize in Chemistry.