In the title salt [systematic name: 4-(3-carboxy-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinolin-7-yl)piperazin-1-ium nitrate], C16H19FN3O3+·NO3−, proton transfer from nitric acid to the N atom of the piperazine ring of norfloxacin has occurred to form a molecular salt. In the extended structure, N—H...O hydrogen bonds link alternating cations and anions into [100] chains, which are reinforced by aromatic π–π stacking interactions between the quinoline moieties of the norfloxacinium cations.
