Franx was born on 20 July 1960 in Eindhoven. He studied astronomy at Leiden University and graduated cum laude in 1984. Four years later he obtained his doctorate from the same university. From 1988 to 1991 Franx was a Junior Fellow of Harvard University. In 1991 he became a Hubble Fellow. Between 1993 and 1998 he was professor of astronomy at the University of Groningen, he then moved to Leiden University where he has held the same position since.
