Abstract. The megamouth shark (Lamniformes, Megachasmidae) is one of four extant planktivorous elasmobranch lineages, but its fossil record is quite limited. In the present study, we report a new discovery of a rare megachasmid shark fossil from the late Miocene—early Pleistocene interval of Okinawa Island, Japan. To date, this specimen represents the only reliable record of a megachasmid fossil from Asia.