In the title compound, [Zn2(C8H4O6)(C12H8N2)2(H2O)6](C8H4O6), the complete ions of both the binuclear dication and the dianion are generated by crystallographic inversion symmetry. The Zn atom is bonded to an N,N'-bidentate phenanthroline ligand, three water moleules and an O-mono-denate 2,5-dihy-droxy-terephthalate dianion. In the resulting distorted octa-hedral ZnN2O4 coordination poly-hedron, the water O atoms are in a mer orientation. Two intra-molecular O-H⋯O hydrogen bonds occur in the bridging 2,5-dihy-droxy-terephthalate dianion within the complex cation and also in the free dianion. An intra-molecular Ow-H⋯O (w = water) hydrogen bond also occurs within the dication. In the crystal, O-H⋯O hydrogen bonds link the component ions into a three-dimensional network.