The book contains an introduction into the theory of Riemann surfaces using a sheaf theoretic approach. Sheaf theory is developed completely. The cohomology of sheaves is introduced by means of the canonical flabby resolution of Godement. The Riemann-Roch theorem is proved for vector bundles. Abel's theorem and the Jacobi inversion theorem are treated. As application, dimension formulae for vector valued automorphic forms in one variable are proved. The necessary tools from topology and algebra are described completely but highly focussed.