The Japanese squirrel is a tree squirrel in the genus Sciurus endemic to Japan. It was described by Dutch zoologist Coenraad Jacob Temminck in 1844. The Japanese squirrel's range includes the islands of Honshū, Shikoku, and Kyūshū. Recently, populations on south-western Honshū and Shikoku decreased, and those on Kyūshū disappeared. One of the factors affecting the local extinction of this species seems to be forest fragmentation by humans.