Bernhard Riemann
Georg Friedrich Bernhard Riemann (September 17, 1826 – July 20, 1866) was an influential German mathematician who made lasting contributions to analysis, number theory and differential geometry, some of them enabling the later development of general relativity.
Read more about Bernhard Riemann: Influence, Euclidean Geometry Versus Riemannian Geometry, Higher Dimensions, Writings in English