The polymeric structure of the title compound, poly[[diaquabis([mu]-biphenyl-4,4'-disulfonato)tetrapotassium(I)] dihydrate], {[K2(C12H8O6S2)(H2O)]爲O}n, is based on an asymmetric unit comprising three independent and different potassium centres, one six-coordinate [K-O = 2.657 (3)-2.866 (5) ŝ, one seven-coordinate [K-O = 2.703 (3)-3.040 (4) ŝ, and the third ten-coordinate [K-O = 2.751 (3)-3.079 (4) ŝ, with two of these lying on crystallographic mirror planes. The four half-occupancy water molecules also lie on the mirror planes with two coordinated (one monodentate, the other bidentate bridging) and two as molecules of solvation. The interlinked coordination polyhedra form chains which are joined laterally through the biphenyl residues as well as through head-to-tail water hydrogen-bonding interactions, giving a two-dimensional structure.