Pine is the common name for any species belonging to the genus Pinus, a member of the family Pinaceae, coniferous trees with needle-like leaves. Pinaceae is the largest family of conifers, consisting of about 262 species, and includes fir, larch, spruce, hemlock, cedar and Douglas fir.

Pine trees are gymnosperms, nonflowering plants that produce exposed seeds not enclosed in an ovary. They are monoecious, bearing gametes of both sexes on the same tree. These gametes are housed in a structure called a strobilus, or cone. Female pinecones are generally found in the upper branches of the tree crown, above the male cone. This reduces the possibility of self-fertilization by the wind-borne male gametes.

The female pinecone, or megastrobilus, produces the ovule, or unfertilized seed. Scales (modified leaves) on the female cone open to receive pollen, then close. Fertilization takes place late the following spring. Over a two to three year period after fertilization, the woody female pinecone develops. In some species, the cones open at maturity and the seeds are released. In others the cones remain closed for several years until opened by rotting, by food-seeking animals, or by fire. In some pines the scale bearing the nutlike seed may be expanded to form a wing for airborne dispersal.

Some pine trees produce seeds, pine nuts (pignons, piñons, pignoli) that are popular in human cuisine. Although most nuts are technically fruits, pine nuts are not because they are not formed by a flowering plant (and pines are not flowering plants). Piñons from pines in the western USA have historically been an important food source for Native Americans. The stone pine (P. pinea) in Italy has been prized since ancient Rome for its pignoli, which are still used for food.

Pine trees are found worldwide, primarily in northern temperate regions. Typically they have woody stems covered in bark, which protects tissues that conduct nutrients and water. When harvested, they provide materials like lumber, turpentine, rosin, paper, and pulp, fuel.