Piperine, an organic compound classed either with the lipid family (a group consisting of fats and fatlike substances) or with the alkaloids, a family of nitrogenous compounds with marked physiological properties. It is one of the sharp-tasting constituents of the fruit of the pepper vine (Piper nigrum).

Piperine is the alkaloid responsible for the pungency of black pepper and long pepper, along with chavicine (an isomer of piperine). It has also been used in some forms of traditional medicine and as an insecticide.

The sharp flavour of freshly ground pepper is attributed to the compound chavicine, a geometric isomer (having the same molecular formula but differing in structure) of piperine. The loss of pungency of ground pepper on storage is associated with slow transformation of chavicine into piperine.