A synergetic study that utilized anion photoelectron spectroscopy and high-level ab initio calculations has explored the activation of H2O molecules by ThO2- molecular anions. Both experiment and theory found conclusive evidence for said activation. In the experiments, this appeared as a tell-tale directional shift in the spectral profile of the anionic complex that ruled out physisorption, i.e., ThO2-(H2O), and implied chemisorption. In the computations, good agreement was found between the calculated and measured vertical detachment energies, and the atomic connectivity (the structure) of the resulting anionic complex was found to be [OTh(OH)2]-.