Transition metal-catalyzed water oxidation reaction is widely studied as an oxidation half reaction of artificial photosynthesis. To date, various investigations of model reaction systems under thermal conditions have been performed, but most of the studies have been carried out with cerium(IV) salts as oxidants under acidic conditions. Herein we report a novel reaction system based on the combination of triarylaminium radicals as oxidants and pyridines as bases, where some ruthenium complexes work as effective catalysts. We believe the novel reaction system described in this paper provides a new approach to develop effective water oxidation catalysts.