Firs (Abies) are a genus of 48–55 species of evergreen conifers in the family Pinaceae. They are found through much of North and Central America, Europe, Asia, and North Africa, occurring in mountains over most of the range. Firs are most closely related to the cedars (Cedrus); Douglas-firs are not true firs, being of the genus Pseudotsuga.

All are trees, reaching heights of 10–80 m (30–260 ft) tall and trunk diameters of 0.5–4 m (2–12 ft) when mature. Firs can be distinguished from other members of the pine family by their needle-like leaves, attached to the twig by a base that resembles a small suction cup; and by erect, cylindrical cones 5–25 cm (2–10 in) long that disintegrate at maturity to release the winged seeds. Identification of the species is based on the size and arrangement of the leaves, the size and shape of the cones, and whether the bract scales of the cones are long and exserted, or short and hidden inside the cone.

The wood of most firs is considered unsuitable for general timber use, and is often used as pulp or for the manufacture of plywood and rough timber. Because this genus has no insect or decay resistance qualities after logging, it is generally recommended for construction purposes as indoor use only (e.g. indoor drywall framing). This wood left outside cannot be expected to last more than 12 to 18 months, depending on the type of climate it is exposed to. It is commonly referred to by several different names, including North American timber, SPF (spruce, pine, fir) and whitewood.