Stanisław Saks (1897 — 1942) was a Polish mathematician and university tutor, known primarily for his membership in the Scottish Café circle, an extensive monograph on the Theory of Integrals, his works on measure theory and the Vitali-Hahn-Saks theorem.
Stanisław Saks was born December 30, 1897 in Kalisz, then part of the German Empire, to an assimilated Polish-Jewish family. In 1915 he graduated from a local gymnasium and joined the newly-recreated Warsaw University. In 1922 he received a doctorate of his alma mater with a prestigious award Cum Maxima Laude. Soon afterwards he also passed his habilitation and received the Rockefeller scholarship, which allowed him to travel to the United States. Around that time he started publishing articles in various mathematical journals, mostly the Fundamenta Mathematicae, but also in the American Transactions of American Mathematical Society. He participated in the Silesian Uprisings and was awarded the Cross of the Valorous and the Medal of Independence for his bravery. Following the end of the uprising he returned to Warsaw and resumed his academic career.
For most of it he studied the theories of functions and functionals in particular. In 1930 he published his most notable book, the Zarys teorii całki (Sketch on the Theory of the Functional), which later got expanded and translated into several languages, including English (Theory of the Integral), French (Théorie de l'Intégrale) and Russian (Teoriya Integrala). Despite his successes, Saks was never awarded with the title of a professor and remained an ordinary tutor, initially at his alma mater and the Warsaw University of Technology, and later at the Lwów University and Wilno University. He was also an active socialist and a journalist at the Robotnik weekly (1919-1926) and later a collaborator of the Association of Socialist Youth.
After the outbreak of World War II and the occupation of Poland by the Nazis, Saks joined the Polish underground. Arrested in November of 1942, he was executed November 23, 1942 by the German Gestapo in Warsaw.