Allylbenzene or 3-phenylpropene is an organic compound with the formula C₆H₅CH₂CH=CH₂. It is a colorless liquid. The compound consists of a phenyl group attached to an allyl group. Allylbenzene isomerizes to trans-propenylbenzene.

In plant biochemistry, the allylbenzene skeleton is the parent (simplest representation) of many phenylpropanoids. Known allylbenzenes include eugenol, safrole, elemicin, myristicin, apiole, dillapiole, chavicol, sarisan, croweacin, osmorhizole, exalatacin, chavibetol, asarone and many others.