Donald Barr (August 8, 1921 – February 5, 2004) was an American educator, writer, and Office of Strategic Services (OSS) officer during World War II. Born in Manhattan, New York, he majored in mathematics and anthropology at Columbia University, graduating in 1941. Following his military service, Barr worked as an administrator at Columbia University before becoming headmaster of the prestigious Dalton School in New York City from 1964 to 1974. He later served as headmaster of the Hackley School in Tarrytown, New York. Barr was also a science fiction novelist, authoring 'Space Relations: A Prince's Tale' (1973) and 'A Planet in Arms' (1981). He wrote nonfiction books for children, including 'The How and Why Wonder Book of Atomic Energy' (1961) and 'The How and Why Wonder Book of Building' (1964). His sons include former U.S. Attorney General William Barr and physicist Stephen Barr.