Tamiasciurus douglasii
Tamiasciurus hudsonicus

Pine squirrels are squirrels of the genus Tamiasciurus. Currently only two species are classified in this genus, the American Red Squirrel T. hudsonicus and the Douglas Squirrel T. douglasii. Both are native to North America: pine squirrrels can be found in the northern and western United States, most of Canada and Alaska.

Pine squirrels are small tree squirrels with bushy tails, and apart from the members of the genus Sciurus, they are probably the members of the large family Sciuridae that conform most closely to the commonly held idea of what a squirrel looks like and how it behaves.

The American Red Squirrel should not be confused with the Eurasian Red Squirrel, Sciurus vulgaris - both are usually just referred to as the "red squirrel" in their home continents.

In southeastern Arizona there is a relict population of T. hudsonicus considered sufficiently distinct to be awarded sub-species status, T. hudsonicus grahamenis, the Mount Graham Pine Squirrel, reduced to a few hundred members on the Madrean sky islands conifer forests at higher, cooler altitudes. They are the southernmost of the entire species, left stranded when desertification reduced the area of conifer forest that existed in glacial times. Some authors treat the Mount Graham Pine Squirrel as a distinct species, T. grahamensis.