The asymmetric unit of the title compound, C(9)H(9)N(2) (+)·0.5C(8)H(4)O(4) (-)·H(2)O, contains one 2-phenyl-imidazolium cation, half a benzene-1,3-dicarboxyl-ate anion and one water mol-ecule. In the crystal, components are connected by N-H⋯O and O-H⋯O hydrogen-bonding inter-actions into a three-dimensional network.