The crystal structure of the title compound, K+.C6H4NO6S-, is built up from p-nitrophenyl sulfate anions and potassium cations. Adjacent anions form dimers, which are linked together in a three-dimensional network via short C-H...O contacts. The coordination sphere of the K+ ions may be described as a distorted square antiprism. The crystal structure is further stabilized by pi-pi stacking interactions between the aryl rings.