**Stefan
Banach** (March 30, 1892 – August 31, 1945) was a Polish
mathematician who is generally considered to have been one of the 20th
century's most important and influential mathematicians. Banach was the
founder of modern functional analysis and a founder 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.