Toluene is a clear liquid aromatic hydrocarbon with a distinctive smell. Its chemical formula is C6H5CH3. Also called methylbenzene or phenylmethane, it is used as an octane booster in fuel, as a solvent in paints and paint thinners, rubber, printing, adhesives, cosmetics, fingernail polish, lacquers, leather tanning and perfumes, and to produce phenol and TNT. It is also used as a raw material for toluene diisocyanate, which is used in the manufacture of polyurethane foams.

Toluene occurs naturally in crude oil and in the tolu tree. It is also produced in the process of making gasoline and other fuels from crude oil and making coke from coal.