In the structure of title compound, [Rb(C(7)H(4)NO(5))(H(2)O)](n), the centrosymmetric cyclic dimeric repeating unit comprises two irregular RbO(4) complex centres bridged by the carboxyl-ate groups of the 5-nitro-salicylate ligands. The coordination about each Rb atom is completed by a monodentate water mol-ecule and a phenolic O-atom donor which gives a bridging extension [Rb-O range = 3.116 (7)-3.135 (5) Å]. The polymeric structure is stabilized by inter-molecular water O-H⋯O(carboxyl-ate) hydrogen bonds and weak inter-ring π-π inter-actions [minimum ring centroid separation = 3.620 (4) Å]. An intramolecular O-H⋯O hydrogen bond between phenol and carboxylate groups is also present.