Atomically precise, inherently charged Au(25) clusters are an exciting prospect for promoting catalytically challenging reactions, and we have studied the interaction between CO(2) and Au(25). Experimental results indicate a reversible Au(25)-CO(2) interaction that produced spectroscopic and electrochemical changes similar to those seen with cluster oxidation. Density functional theory (DFT) modeling indicates these changes stem from a CO(2)-induced redistribution of charge within the cluster. Identification of this spontaneous coupling led to the application of Au(25) as a catalyst for the electrochemical reduction of CO(2) in aqueous media. Au(25) promoted the CO(2) → CO reaction within 90 mV of the formal potential (thermodynamic limit), representing an approximate 200-300 mV improvement over larger Au nanoparticles and bulk Au. Peak CO(2) conversion occurred at -1 V (vs RHE) with approximately 100% efficiency and a rate 7-700 times higher than that for larger Au catalysts and 10-100 times higher than those for current state-of-the-art processes.