Antoni Zygmund was a Polish mathematician. He is considered one of the greatest analysts of the 20th century. His main area of interest was harmonic analysis. He was born on December 25, 1900, Warsaw, Poland. Zygmund graduated from the University of Warsaw (Ph.D. 1923) and taught there (1926–29) and at the Polytechnical School in Warsaw (1922–29). After a year in England on a Rockefeller fellowship, he became professor of mathematics at the University of Wilno. In 1940, following a period of service in the Polish army, he fled his war-scarred homeland to the United States. After successive posts at Mount Holyoke College and the University of Pennsylvania, Zygmund joined the faculty of the University of Chicago, where he remained until his retirement in 1980. In 1986 he received the U.S. National Medal of Science for creating the so-called Chicago School of Analysis, which focused on Fourier analysis and its applications to partial differential equations. He wrote Trigonometric Series (1935), Analytic Functions (1938, with Stanislaw Saks), and Measure and Integral (1977). Zygmund held membership in the national academies of science of the United States, Poland, Argentina, and Spain.