In the structure of the title compound, C28H16O6·H2O [systematic name 3,11-bis(4-hydroxyphenyl)-4,12-dioxapentacyclo[22.214.171.124,5.013,17.09,18]octadeca-1(16),2,5(18),6,8,10,13(17),14-octaene-7,15-diol monohydrate], the hopeahainol C molecule lies about an inversion center with the solvent water molecule located on a crystallographic twofold axis. Hopeahainol C is an oligostillbenoid compound and was isolated from the bark of Shorea roxburghii G. Don. The five central fused rings are essentially planar with an r.m.s. deviation of 0.0173 (3) Å. The 4-hydroxyphenyl ring is twisted with respect to this plane, with the dihedral angle between the phenyl ring and the fused-ring system being 41.70 (10)°. The crystal features intermolecular O—H⋯O hydrogen bonds. These interactions link the hopeahainol C molecules into chains along the b axis. Water molecules are located interstitially between the hopeahainol C molecules linked by O(water)—H⋯O(hydroxy) and O(hydroxy)—H⋯O(water) hydrogen bonds. π–π interactions are also observed with centroid–centroid distances of 3.6056 (17) and 3.5622 (17) Å. Short O⋯O contacts [2.703 (2)–2.720 (3) Å] are also present in the crystal.