The presence of water can strongly affect the reactivity of gold catalysts. For this reason, ab initio density functional simulations have been performed to study the adsorption and dissociation of water on the anatase-TiO2(101) surface, both clean and in the presence of a supported model gold nanocluster, Au-4. When adsorbed not too close to the cluster, water is adsorbed and dissociated with roughly the same binding energies and dissociation barriers as in the catalyst-free surface. If the molecule adsorbs at the Au/TiO2 perimeter interface, making contact with gold, we find a slight stabilization of molecular water, whereas dissociated water becomes slightly less stable. The preferential mechanism for water dissociation is found to be a splitting of the H-OH bond at the TiO2 surface, with the gold cluster playing a minor role. Calculations of the relative stability of various water-related species show that the gold catalyst favours accumulation of excess hydroxyls around its perimeter.