In-situ generation of the carbon dioxide radical anion (CO2 •-) using mild reaction conditions is a general goal for the activation of organic molecules. CO2 •-can be accessed photochemically via hydrogen-atom abstraction from formate (HCO2 -) or electrochemically by CO2 reduction. Once generated, CO2 •-enables a variety of follow-up organic reactions, including hydrodehalogenation, carboarylation, oxyarylation, radical deamination, aldehyde reduction, Birch reduction, sulfonamide cleavage, and the carboxylation (or decarboxylation) of a wide variety of unsaturated C-C bonds. In each of the aforementioned examples, CO2 •-functions either as a single electron transfer (SET) reductant or as a nucleophile, depending on the formal reduction potential (E 0' ) and the electrophilicity of the organic substrate.