Natural rubber; also called India rubber or caoutchouc; as initially produced; consists of polymers of the organic compound isoprene; with minor impurities of other organic compounds plus water.

The major commercial source of natural rubber latex is the Par?rubber tree (Hevea brasiliensis); a member of the spurge family; Euphorbiaceae. This species is widely used because it grows well under cultivation and a properly managed tree responds to wounding by producing more latex for several years.