Terphenyls are a group of closely related aromatic hydrocarbons. Also known as diphenylbenzenes or triphenyls, they consist of a central benzene ring substituted with two phenyl groups. There are three substitution patterns: ortho-terphenyl, meta-terphenyl, and para-terphenyl. Commercial grade terphenyl is generally a mixture of the three isomers. This mixture is used in the production of polychlorinated terphenyls, which were formerly used as heat storage and transfer agents.

p-Terphenyl derivatives are found in various fungi and bacteria. One example is atromentin, a pigment found in some mushrooms. These natural p-terphenyls are better described as diphenylquinones or diphenylhydroquinones. Some m-terphenyl compounds occur in plants.