Antoni Zygmund (December 25, 1900 – May 30, 1992) was a Polish born American mathematician who exerted a major influence on 20th-century mathematics.
Born in Warsaw, Zygmund was professor at the University of Wilno from 1930 until 1939. During the occupation of Poland (Second World War), he emigrated to USA in 1940 and became professor at the Mount Holyoke College in South Hadley. From 1945 until 1947 he was professor at the University of Pennsylvania and from 1947 at the University of Chicago.
He was member of several scientific societies. From 1930 until 1952 member of the Friends of Science Society (TNW), since 1946 member of Polish Academy of Skills (PAU), since 1959 member of Polish Academy of Sciences (PAN) and since 1961 member of the National Academy of Science in Washington. He received the National Medal of Science in 1986.
His main interest was harmonic analysis. He wrote a standard two-volume work Trigonometric Series. His students included Alberto Calderón, Paul Cohen, Nathan Fine and Elias Stein. He died in Chicago.
His work has had pervasive influence in many fields of mathematics, particularly in mathematical analysis. Perhaps most important was his work with Calderón on singular integral operators.