Poly[diaqua-bis(μ(3)-1H-benzimidazole-5,6-dicarboxyl-ato-κN:O,O:O)bis-(μ(2)-1H,3H-benzimidazolium-5,6-dicarboxyl-ato-κO,O:O)digadolinium(III)].

In the title complex, [Gd(2)(C(9)H(4)N(2)O(4))(2)(C(9)H(5)N(2)O(4))(2)(H(2)O)(2)](n), two of the benzimidazole-5,6-dicarboxyl-ate ligands are pro-ton-ated at the imidazole groups. Each Gd(III) ion is coordinated by six O atoms and one N atom from five ligands and one water mol-ecule, displaying a distorted bicapped trigonal-prismatic geometry. The Gd(III) ions are linked by the carboxyl-ate groups and imidazole N atoms, forming a layer parallel to (001). These layers are further connected by O-H⋯O and N-H⋯O hydrogen bonds into a three-dimensional supra-molecular network.