The asymmetric unit of the title compound [systematic name: 4,4′-bipyridinium bis(2,3-dihydro-1,1,3-trioxo-1,2-benzothiazolate) dihydrate], C10H10N2+·2C7H4NO3S−·2H2O, consists of one half of a 4,4′-bipyridinium cation, which has inversion symmetry, one saccharinate anion and one water molecule. These ions and molecules are further linked into a supramolecular structure by intermolecular hydrogen bonds.