Julian Lowell Coolidge (September 28, 1873 - March 5, 1954) was an American mathematician and a professor and chairman of the Harvard University Mathematics Department.
Born in Brookline, Massachusetts, he graduated from Harvard University and Oxford University.
Between 1897 and 1899 Julian Coolidge taught at the prestigious Groton School where one of his students was Franklin D. Roosevelt. He left the prestigious private school to accept a teaching position at Harvard and in 1902 was given an assistant professorship, but took two years off to further his education with studies in Turin, Italy before receiving his doctorate from the University of Bonn. Julian Coolidge then returned to teach at Harvard where he remained for his entire academic career, interrupted only by a year at the Sorbonne in Paris as an exchange professor.
During World War I, he served with the U.S. Army's Overseas Expeditionary Force in France, rising to the rank of major. At the end of the war, the government of France awarded him the Legion of Honor.
Coolidge returned to teach at Harvard where he was awarded a full professorship. In 1927 he was appointed chairman of the Mathematics Department at Harvard, a position he held until his retirement in 1940. A Fellow of the American Academy of Arts and Sciences, Coolidge served as vice-president of the Mathematical Association of America and the American Mathematical Society. He authored several books on mathematics and on the history of mathematics.
Julian Coolidge died in 1954 in Cambridge, Massachusetts, aged 80.
J. L. Coolidge (1916) A treatise on the circle and the sphere, Oxford University Press