Natural rubber, also called India Rubber or caoutchouc, is an elastomer (an elastic hydrocarbon polymer) that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined into a usable rubber. The purified form of natural rubber is the chemical polyisoprene, which can also be produced synthetically. Natural rubber is used extensively in many applications and products, as is synthetic rubber. It is normally very stretchy and flexible and extremely waterproof.

The commercial source of natural rubber latex is the Pará rubber tree (Hevea brasiliensis), a member of the spurge family, Euphorbiaceae. This species is widely used because it responds to wounding by producing more latex.

Other plants containing latex include gutta-percha (Palaquium gutta), rubber fig (Ficus elastica), Panama rubber tree (Castilla elastica), spurges (Euphorbia spp.), lettuce, common dandelion (Taraxacum officinale), Russian dandelion (Taraxacum kok-saghyz), Scorzonera (tau-saghyz), and guayule (Parthenium argentatum). Although these have not been major sources of rubber, Germany attempted to use some of these during World War II when it was cut off from rubber supplies^{[citation needed]}. These attempts were later supplanted by the development of synthetic rubbers. To distinguish the tree-obtained version of natural rubber from the synthetic version, the term gum rubber is sometimes used.