### Abstract

The spectral correlations of large well-connected quantum graphs are shown to behave according to the predictions of random-matrix theory by using a supersymmentry method. In a first (generally applicable) step the energy-average over the spectrum of individual graphs can be traded for the functional average over a supersymmetric nonlinear sigma-model action. Reducing the full sigma-model to its mean field theory is equivalent to the random-matrix theory of the Wigner-Dyson ensembles. Conditions for the validity of a mean field description will be discussed along with the stability of the universal random matrix behavior with regard to perturbations.