The **Riemann zeta function** or **Euler–Riemann zeta function**, *ζ*(*s*), is a function of a complex variable *s* that analytically continues the sum of the infinite series

which converges when the real part of *s* is greater than 1. More general representations of *ζ*(*s*) for all *s* are given below. The Riemann zeta function plays a pivotal role in analytic number theory and has applications in physics, probability theory, and applied statistics.

As a function of a real variable, Leonhard Euler first introduced and studied it in the first half of the eighteenth century without using complex analysis, which was not available at the time. Bernhard Riemann‘s 1859 article “On the Number of Primes Less Than a Given Magnitude” extended the Euler definition to a complex variable, proved its meromorphic continuation andfunctional equation, and established a relation between its zeros and the distribution of prime numbers.^{[2]}

The values of the Riemann zeta function at even positive integers were computed by Euler. The first of them, *ζ*(2), provides a solution to the Basel problem. In 1979 Apéry proved the irrationality of *ζ*(3). The values at negative integer points, also found by Euler, are rational numbers and play an important role in the theory of modular forms. Many generalizations of the Riemann zeta function, such as Dirichlet series, Dirichlet L-functions and L-functions, are known.

In mathematics, the **Riemann hypothesis** is a conjecture that the Riemann zeta function has its zeros only at the negative even integers and the complex numbers with real part 1/2. It was proposed by Bernhard Riemann (1859), after whom it is named. The name is also used for some closely related analogues, such as the Riemann hypothesis for curves over finite fields.

The Riemann hypothesis implies results about the distribution of prime numbers. Along with suitable generalizations, some mathematicians consider it the most important unresolved problem in pure mathematics (Bombieri 2000). The Riemann hypothesis, along with Goldbach’s conjecture, is part of Hilbert’s eighth problem in David Hilbert‘s list of 23 unsolved problems; it is also one of the Clay Mathematics Institute‘s Millennium Prize Problems.

The Riemann zeta function ζ(*s*) is a function whose argument *s* may be any complex number other than 1, and whose values are also complex. It has zeros at the negative even integers; that is, ζ(*s*) = 0 when *s* is one of −2, −4, −6, …. These are called its **trivial zeros**. However, the negative even integers are not the only values for which the zeta function is zero. The other ones are called *non-trivial zeros*. The Riemann hypothesis is concerned with the locations of these non-trivial zeros, and states that:

- The real part of every non-trivial zero of the Riemann zeta function is 1/2.

Thus, if the hypothesis is correct, all the non-trivial zeros lie on the **critical line** consisting of the complex numbers 1/2 + *i t*, where *t* is areal number and *i* is the imaginary unit.

There are several nontechnical books on the Riemann hypothesis, such as Derbyshire (2003), Rockmore (2005), (Sabbagh 2003a,2003b), du Sautoy (2003). The books Edwards (1974), Patterson (1988), Borwein et al. (2008) and Mazur & Stein (2015) give mathematical introductions, while Titchmarsh (1986), Ivić (1985) and Karatsuba & Voronin (1992) are advanced monographs.