Abstract. A proof of the Riemann hypothesis is obtained for zeta functions constructed in Fourier analysis on locally compact skew–fields. The skew–fields are the algebra of quater-nions whose coordinates are real numbers and the algebra of quaternions whose coordinates are elements of a p–adic field for every prime p. Fourier analysis is also applied in locally compact algebras which are finite Cartesian products of locally compact skew–fields and in quotient spaces defined by a summation originating in the construction of Jacobian theta functions. The Riemann hypothesis is a consequence of the maximal accretive property of a Radon transformation relating Fourier analysis on a locally compact skew–field with Fourier analysis on a maximal c...