Reinhard Genzel is a German astrophysicist and director at the Max Planck Institute for Extraterrestrial Physics in Garching, a professor at Ludwig Maximilian University of Munich, and an emeritus professor at the University of California, Berkeley. He was awarded one quarter of the 2020 Nobel Prize in Physics, shared with Andrea Ghez, 'for the discovery of a supermassive compact object at the centre of our galaxy,' with the other half going to Roger Penrose. Over nearly three decades Genzel and his group tracked the orbits of individual stars circling Sagittarius A* at the heart of the Milky Way using ever more sophisticated infrared and adaptive-optics instruments, demonstrating that the stars orbit an unseen object of about four million solar masses confined to a tiny volume — the most compelling empirical evidence that the object is a supermassive black hole. His teams built pioneering ground- and space-based instruments, including SHARP, SINFONI, and the GRAVITY interferometer combining the four 8-metre telescopes of the ESO Very Large Telescope, which in 2018 measured the gravitational redshift of the star S2 at pericentre, confirming a prediction of general relativity near a black hole. Genzel also studies the formation and evolution of galaxies. Trained in radio astronomy at the Max Planck Institute for Radio Astronomy, he is a foreign member of the Royal Society and a recipient of the Crafoord Prize.