<p>Understanding the factors underlying the interaction of water with oxide surfaces is of high technological importance for applications ranging from nuclear fuel safety to heterogeneous catalysis. However, it is a complex task as numerous different factors (related to the surface and bulk properties) are involved. In the present study, we investigated the characteristics of water adsorption (quantities adsorbed and energetics) on binary oxides of fluorite structure and their mixed oxide combinations (solid solutions). Three representative oxides were chosen, differing in lattice parameter (ionic radius) and oxidation state: ThO₂ which has a very stable Th⁴⁺ cation, CeO₂ in which the cerium cations can be easily reduced to Ce³⁺, and UO₂ in which the uranium cations tend to further oxidize to U⁵⁺ and U⁶⁺. Based on the H₂O adsorption isotherms and enthalpies of adsorption versus coverage, combined with X-ray photoelectron spectroscopy (XPS) study of the oxide surface, the main factors underlying the characteristics of water adsorption on the fluorite oxides were identified. The present work points to the importance of oxygen hyper-stoichiometry (in U-containing oxides) on the interaction of water with the oxide's surface. Furthermore, correlations between Fermi level positioning and water dissociation tendencies are established. This work advances our understanding of water-oxide interactions with implications for material design in energy and environmental systems.</p> Graphical Abstract <p></p>