10 May Stefan Banach
Dead: 31 August 1945
He was a Polish mathematician who is generally considered one of the world's most important and influential 20th-century mathematicians.
He was the founder of modern functional analysis, and an original member of the Lwów School of Mathematics.
His major work was the 1932 book, Théorie des opérations linéaires (Theory of Linear Operations), the first monograph on the general theory of functional analysis.