A new sesquiterpenoid, ar-tumerdiol (1) as well as ar-tumerone (2), α-tumerone (3), β-tumerone (4), 4-(1′ ,5′ -dimethyl-3′-oxo-4′-hexenyl)-2-cyclohexen-1-one (5), turmeronol (6), curcumin (7), and hexahydrocurcumin (8), were isolated from the rhizomes of Curcuma longa (Zingiberaceae). The structure of the new sesquiterpenoid was elucidated by chemical and physical evidence.