Naphtha, any of various volatile, highly flammable liquid hydrocarbon mixtures used chiefly as solvents and diluents and as raw materials for conversion to gasoline. Naphtha was the name originally applied to the more volatile kinds of petroleum issuing from the ground in the Baku district of Azerbaijan and Iran. As early as the 1st century AD, naphtha was mentioned by the Greek writer Dioscorides and the Roman writer Pliny the Elder. Alchemists used the word principally to distinguish various mobile liquids of low boiling point, including certain ethers and esters.

In modern usage the word naphtha is usually accompanied by a distinctive prefix. Coal-tar naphtha is a volatile commercial product obtained by the distillation of coal tar. Shale naphtha is obtained by the distillation of oil produced from bituminous shale by destructive distillation. Petroleum naphtha is a name used primarily in the United States for petroleum distillate containing principally aliphatic hydrocarbons and boiling higher than gasoline and lower than kerosene.