1849 – 1925
Felix Klein was a German mathematician renowned for his work in group theory, complex analysis, and non-Euclidean geometry. He is best known for the Erlangen Program, which classified geometries by their underlying symmetry groups, profoundly influencing both mathematics and the philosophy of geometry.
Formulated the Erlangen Program classifying geometries via group theory
Pioneered work on non-Euclidean geometry and its philosophical implications
Made foundational contributions to the theory of Riemann surfaces
Developed the Klein bottle as a non-orientable surface
Advocated for reform in mathematics education internationally