Stefan Banach was a Polish mathematician born on March 30, 1892, in Kraków, Poland. He is best known for founding the field of functional analysis, which studies spaces of functions and their properties. His work laid the groundwork for many modern mathematical theories and applications. Banach is also famous for the Banach space, a concept that describes a complete normed vector space. He contributed significantly to various areas of mathematics, including measure theory and topology. Banach passed away on August 31, 1945, but his influence continues to shape mathematics today.