Cerium suboxide clusters are a recent catalyst class that has received interest for the generation of H<sub>2</sub> from water. Using density functional theory calculations, this work examines the reaction of Ce<sub>2</sub>O<sup>–</sup> clusters with H<sub>2</sub>O. It is shown that the reaction can proceed along both doublet and quartet pathways. In both cases, hydrogen formation is facilitated by intermediate structures featuring bridging hydride and hydroxide ligands. Interestingly, it is shown that metal d electrons facilitate the reduction of water. This work provides new understanding of this reaction and provides new insight into the reactivity of small lanthanide-based clusters with water.<br>