either of two colourless liquid hydrocarbons, α-pinene and β-pinene, occurring as major components of the essential oil of pine trees and used as a chemical raw material. Both compounds belong to the isoprenoid series and have the molecular formula C₁₀H₁₆. They often occur together and are separated by fractional distillation.

The principal source of α-pinene is turpentine obtained in the sulfate process for making paper. The commercial product is 90–95 percent pure. Large amounts of α-pinene are converted to synthetic pine oil or to camphene, which is chlorinated to toxaphene, an insecticide, or treated with acetic acid to form isobornyl acetate, a perfume with a pine-needle aroma and an intermediate in synthetic camphor manufacture.