reaction mechanism of photo‐induced DNA cleavage in nature, a C(sp3)−H cyanation reaction promoted by visible‐light photoredox/phosphate hybrid catalysis was developed. Phosphate radicals, generated by one‐electron photooxidation of phosphate salt, functioned as a hydrogen‐atom‐transfer catalyst to produce nucleophilic carbon radicals from C(sp3)−H bonds with a high bond‐dissociation energy. The resulting