Charge transport in organic crystals The understanding of charge transport is one of the central goals in the research on semiconducting crystals. For organic crystals this is particularly complicated due to the strength of the electron phonon interaction which requires the description of a seamless transition between the limiting cases of a coherent band transport mechanism and incoherent hopping. In this thesis charge transport phenomena in organic crystals are studied by theoretical means. A theory for charge transport in organic crystals is developed which covers the whole temperature range from low T where it reproduces an expression from the Boltzmann equation for band transport via elevated T where it generalizes Holsteins small polaron theory to finite bandwidths up to high T for which a temperature dependence equal to Marcus electron transfer theory is obtained. Thereby coherent band transport and thermally induced hopping are treated on equal footing while simultaneously treating the electron phonon interaction non perturbatively. By avoiding the approximation of narrow polaron bands the theory allows for the description of large and small polarons and serves as a starting point for computational studies.