Hexahydroxydiphenic acid is an organic compound with the formula [(HO)<sub>3</sub>C<sub>6</sub>HCO<sub>2</sub>H]<sub>2</sub>. It is the oxidatively coupled derivative of gallic acid It is a white solid, although samples are typically brown owing to oxidation.
Luteic acid and ellagic acid are the mono- and dilactone of hexahydroxydiphenic acid, respectively. Hexahydroxydiphenic acid is a component of some ellagitannins, such as casuarictin.