Mearns's squirrel (Tamiasciurus mearnsi) is a species of rodent in the family Sciuridae. It is endemic to pine and fir forests at altitudes of 2,100–2,400 metres (6,900–7,900 ft) in central Baja California in Mexico. This endangered species 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. Mearns's squirrel is closely related to the Douglas squirrel, but far less is known about its behavior, which was first studied in detail in 2004-2005.