An elephant molar from Himeshima Island is systematically described in detail. It was collected from sea-bottom very near the coast of the island, and probably occurred from the Early to Middle Pleistocene sediments exposed there. The molar is assigned to a right M₃ of Mammuthus trogontherii, one of primitive mammoth species ancestral to the woolly mammoth, on the basis of its morphological characters. The molar is compared with M₃ of primitive mammoths known from Japan and the adjacent continent. The temporal distribution and migration of M. trogontherii in East Asia are discussed in the light of the data obtained as well as recent knowledge on the species.