A phytochemical investigation of the fruits of Schisandra arisanensis has yielded a novel triterpenoid, arisandilactone A (1). Compound 1 has an unprecedented skeleton having a 5/5/7/5/8/5-fused hexacyclic ring system. The structure of 1 was elucidated by spectroscopic methods, especially 2D NMR techniques (COSY, HMQC, HMBC, and NOESY) and was confirmed by X-ray crystallographic analysis. A plausible biosynthetic pathway for 1 is also discussed.