Czeslaw Ryll-Nardzewski, born on October 7, 1926 and died September 18, 2015, he was a Polish mathematician.
Born in Wilno, Commonwealth of Poland, he was a student of Hugo Steinhaus.
At the age of 26 he became professor at the Warsaw University.
In 1959, he became a professor at the Wroclaw University of Technology.
His main research areas are measure theory, functional analysis, foundations of mathematics and probability theory.
Several theorems bear his name: the Ryll-Nardzewski fixed point theorem, the Ryll-Nardzewski theorem in model theory, and the Kuratowski–Ryll-Nardzewski measurable selection theorem.
He became a member of the Polish Academy of Sciences in 1967.
Czesław Ryll-Nardzewski died in 2015 at the age of 88.