Abies lasiocarpa, the subalpine fir or Rocky Mountain fir, is a western North American fir tree.

Firs are evergreen coniferous trees belonging to the genus Abies in the family Pinaceae. There are approximately 48–65 extant species, found on mountains throughout much of North and Central America, Europe, Asia, and North Africa. The genus is most closely related to Cedrus (cedar). The genus name is derived from the Latin "to rise" in reference to the height of its species. The common English name originates with the Old Norse, fyri, or the Old Danish, fyr.