Uranium (VI) catalyzes the photooxidation of alkanes, alkenes, alcohols, and aldehydes by molecular oxygen in aqueous solution. Despite the mechanistic complexities, each of the reactions investigated yielded a single organic product. On the basis of the quenching kinetics, the deuterium isotope effects, the nature of the products, and linear free energy relationships, all the reactions appear to take place by hydrogen atom abstraction from C-H bonds, followed by uranium-mediated product formation.