Mearns's squirrel (Tamiasciurus mearnsi) is a species of squirrel native to Mexico. It is an endangered species that occurs in low densities and is threatened by habitat loss. It is possibly also threatened by competition from the eastern gray squirrel, which was introduced to the range of Mearns's squirrel in 1946, but may not be present anymore. It is closely related to the Douglas squirrel, but far less is known about its behavior, which was first studied in detail in 2004. It is named for the 19th-century American naturalist Edgar Mearns.