A scincid lizard of the genus Plestiodon from Kuchinoshima Island in the Tokara Group of the Northern Ryukyus, Japan, has proved to be genetically and morphologically differentiated from any previously recognized species in the genus. We thus describe this island population as a new species, Plestiodon kuchinoshimensis. The new species shows characteristics of the P. latiscutatus species group, but differs from other species of this group by the combination of the following character states: postnasal absent; hatchling with five longitudinal light lines on dorsum; lateral light line on each side passing over ear opening and the sixth to eighth scale rows at midbody; dorsolateral light line beginning from behind supraoculars; patch of enlarged irregular scales on posterior femur absent; scale rows around midbody 27–32; and brownish background on the dorsal surface of the juvenile.