Mesodermochelys is an extinct genus of sea turtle known from the Santonian to the Campanian (Late Cretaceous) of what today is Japan. One species is known, the type species M. undulatus; it was given its binomial name by Ren Hirayama and Tsutomu Chitoku in 1996. Studies of its skull indicate that it was a primitive member of the Dermochelyidae (leatherback turtle family) that was closely related to the Protostegidae. It has been described as the best representative of Mesozoic dermochelyids.