Born on July 3, 1941, in Norwich, Ontario, Ronald Crosby Davidson grew up on a dairy farm, learning to drive a tractor by 11. After graduating in 1963 with an undergraduate physics degree from McMaster University in Hamilton, Ontario, he enrolled in the plasma physics program at Princeton. He completed his doctorate in three years. After a postdoctoral fellowship at the University of California, Berkeley, he became a professor at the University of Maryland. He then moved to the Massachusetts Institute of Technology, where he was the founding director of the university’s plasma fusion center. In 1991, he was enticed to move to Princeton, where Harold P. Furth had spearheaded the efforts to build the Tokamak Fusion Test Reactor. Dr. Furth stepped down in 1990 as director of the laboratory because of health problems. After Dr. Davidson left as director, he returned to research, continuing as a professor in Princeton’s astrophysics department until 2011. Dr. Davidson is survived by his wife of 53 years, Jean; a daughter, Cynthia Premru; a son, Ronald Jr.; and four grandchildren.