Michel G. E. Mayor (born January 12, 1942, Lausanne) is a Swiss astrophysicist and professor emeritus at the University of Geneva's Department of Astronomy. He formally retired in 2007, but remains active as a researcher at the Observatory of Geneva. He is co-winner of the 2010 Viktor Ambartsumian International Prize.Together with Didier Queloz in 1995 he discovered 51 Pegasi b, the first extrasolar planet orbiting a sun-like star, 51 Pegasi.

After earning a Master's degree in Physics at the University of Lausanne in 1966, Mayor obtained his doctorate in Astronomy at the Geneva Observatory in 1971. His thesis included an "Essay on the kinematical properties of stars in the solar vicinity: possible relation with the galactic spiral structure." He studied briefly at the University of Cambridge Institute of Astronomy and spent sabbatical semesters at the European Southern Observatory (ESO) in Chile and at the Institute for Astronomy of the University of Hawaii.He received Gold Medal of the Royal Astronomical Society in 2015.