BTEX is an acronym that stands for benzene, toluene, ethylbenzene, and xylenes. These compounds are some of the volatile organic compounds (VOCs) found in petroleum derivatives such as petrol (gasoline). Toluene, ethylbenzene, and xylenes have harmful effects on the central nervous system.

BTEX compounds are notorious due to the contamination of soil and groundwater with these compounds. This typically occurs near petroleum and natural gas production sites, and petrol stations and other areas with Underground Storage Tanks (USTs) or Above-ground Storage Tanks (ASTs) containing gasoline or other petroleum-related products.

The amount of 'Total BTEX', the sum of the concentrations of each of the constituents of BTEX, is sometimes used to aid in assessing the relative risk or seriousness at contaminated locations and the need of remediation of such sites. Naphthalene may be included in Total BTEX analysis yielding results referred to as BTEXN. In the same way, styrene is sometimes added, making it BTEXS.