In this study, we explore the untapped potential of ketocoumarins as photosensitizers for light driven hydrogen evolution. Through the synthesis of a library of novel ketocoumarins and optimization of the reaction conditions, we achieved remarkable turnover numbers nearing 4000 relative to the cobaloxime catalyst. Our spectroscopic and electrochemical studies revealed a reductive quenching mechanism for hydrogen evolution. By increasing the cobaloxime concentration we could successfully prevent photodegradation of the photosensitizer, and we could sustain hydrogen production for up to 22 days. Our work demonstrates that ketocoumarins, with their ease of synthesis and tunability, can serve as efficient and practical alternatives to the commonly used heavy metal-based photosensitizers.