Eucalyptol (also known as Cineol) is a terpene which comprises up to 90% of the essential oil of some species of the generic product eucalyptus oil. Hence the common name of the compound. It is also found in camphor laurel, bay leaves, tea tree, sweet basil, wormwood, rosemary, common sage, Cannabis sativa, and other aromatic plant foliage.

Although it can be used internally as a flavouring and medicine ingredient at very low doses, typical of many essential oils (volatile oils), eucalyptol is toxic if ingested at higher than normal doses.