Achilleol A is a triterpenoid that is (1S)-2,2-dimethyl-4-methylidenecyclohexanol which is substituted at position 3 by a (6E,10E,14E)-2,6,10,15-tetramethylheptadeca-2,6,10,14-tetraen-17-yl group. It was the first monocyclic triterpenoid found in nature and originally isolated from Achillea odorata.