Robert Karplus was born in Vienna, where he lived until the German occupation of Austria in 1938. He emigrated with his mother and brother to escape the Anschluss. After a six-month stay in Switzerland, the family moved to the United States and settled in the Boston area. He entered Harvard University in 1943 and completed his Ph.D at the age of twenty-one. His thesis under E. Bright Wilson was on microwave spectroscopy and included both experimental and theoretical work. He was recognized by those he worked with for his brilliance, originality, energy, and cheerful, positive outlook.