Marcel Golay (1927-2015) was a Swiss astronomer, the eighth director of the Geneva Observatory from 1956 to 1992 and a professor at the University of Geneva. With Fredy Rufener he devised the seven-colour Geneva photometric system, which became a standard tool for the astrophysical study of stars, and he pioneered ultraviolet observation of celestial objects from stratospheric balloons. A builder, he expanded his institution with new facilities at Sauverny. A committed European, he campaigned for Switzerland's entry into the European Space Research Organisation (ESRO, forerunner of ESA) and the European Southern Observatory (ESO). In L'homme et l'espace (1972) he provided the scientific direction of the astronomical section.