A furanolabdane diterpene alcohol was isolated from the rhizomes of the endemic Vietnamese medicinal plant Alpinia tonkinensis Gagnep. (Zingiberaceae). Its absolute stereostructure was established to be (12S)-15,16-epoxy-8(17),13(16),14-labdatrien-12-ol from spectroscopic data and by applying the modified Mosher’s method. It is first report on the natural occurrence and absolute stereochemistry of the diterpene which was previously known as a synthetic intermediate.