六氯环己烷（HCH），俗称六六六、六氯化苯，是环己烷的1,2,3,4,5,6-六氯代衍生物，属于卤代烃类。用作农药。它包括α-、β-、γ-、δ-、ε-异构体，其中γ-六氯环己烷是最重要的异构体，并且是该杀虫剂的活性成分，俗称林丹。

工业品六氯环己烷是通过在光照下将氯气通入纯苯中而制备的。这个过程得到的是六氯环己烷各种异构体的混合物，可以通过利用各异构体在有机溶剂中溶解度的不同，而将高含量的γ-异构体提取出来。

工业品六氯环己烷的组成大致为：α-六氯环己烷（55–60%，甲体）、β-六氯环己烷（5–14%，乙体）、γ-六氯环己烷（12–16%，丙体）、δ-六氯环己烷（6–8%，丁体）、ε-六氯环己烷（2–9%，戊体）、七氯环己烷（4%）、八氯环己烷（0.6%）。

Hexachlorocyclohexane (HCH) is any of several polyhalogenated organic compounds consisting of a six-carbon ring with a chlorine attached to each carbon. There are many isomers for this structure, differing by the stereochemistry of the individual chlorine substituents on the cyclohexane. It is sometimes called erroneously called "benzene hexachloride" (BHC). They have been used as models for analyzing the effects of different geometric positions of the large atoms with dipolar bonds on the stability of the cyclohexane conformation. Some isomers are pesticides.