The Okurodani Formation is an Early Cretaceous geologic formation in central Honshu, Japan. Part of the Tetori Group, it primarily consists of freshwater continental sediments deposited in a floodplain environment, with occasional volcanic tuffite horizons. It has an uncertain age, probably dating between the Hauterivian and Aptian. An indeterminate iguanodontian dinosaur tooth has been recovered from the formation. Many other fossil vertebrates are known from the KO2 locality