The title compound {systematic name: 4-[(E)-2-(3,5-dihy-droxy-phen-yl)ethen-yl]benzene-1,3-diol dihydrate}, C(14)H(12)O(4)·2H(2)O, a derivative of resveratrol, was isolated from mulberry. The linking C=C double bond has a trans conformation and allows the formation of a conjugated system throughout the mol-ecule. The dihedral angle between the benzene rings is 9.39 (9)°. In the crystal, mol-ecules are connected into a three-dimensional architecture through O-H⋯O hydrogen bonds between hy-droxy groups of oxyresveratrol and solvent water mol-ecules.