German mathematician who was a major figure in nineteenth-century mathematics. In many ways, he was the intellectual successor of Gauss. In geometry, he started the development of those tools which Einstein would eventually use to describe the universe and which in the twentieth century would be turned into the theory of manifolds. His basic geometrical ideas were presented in his famous inaugural lecture at Göttingen, to an audience including Gauss. He did much significant work in analysis, in which his name is preserved in the Riemann integral, the Cauchy–Riemann equations and Riemann surfaces. He also made connections between prime number theory and analysis: he formulated the Riemann hypothesis, a conjecture concerning the so-called zeta function, which if proved would give information about the distribution of prime numbers.