An antifungal compound was isolated from methanol extracts of stems and roots of Chloranthus henryi Hemsl. using ethyl acetate extraction and various chromatographic techniques. On the basis of spectroscopic analyses including mass and various NMR, the structure of the compound was identified as a dimeric sesquiterpene, CHE-23C. The compound showed potent antifungal activities (MICs = 1-32 microg/mL) in vitro against various phytopathogenic fungi such as Alternaria kikuchiana , Botrytis cinerea , Colletotrichum lagenarium , Magnaporthe grisea , Pythium ultimum , and Phytophthora infestans . In particular, it exhibited 91 and 100% disease-control activity in vivo against tomato late blight (P. infestans) and wheat leaf rust ( Puccinia recondita ) at concentrations of 33 and 100 microg/mL, respectively. The disease-control activity of this compound was stronger than that of the commercially available fungicide chlorothalonil, but weaker than that of dimethomorph. Therefore, the compound might serve as an interesting lead to develop effective antifungal agents.