IN THE CATION OF THE TITLE SALT (SYSTEMATIC NAME: 5-{5-chloro-3-[4-(methyl-sulfon-yl)phen-yl]-2-pyrid-yl}-2-methyl-pyridinium 2,4,6-trinitro-phenolate), C(18)H(16)ClN(2)O(2)S(+)·C(6)H(2)N(3)O(7) (-), the mean planes of the two pyridine rings in the bipyridine unit are twisted by 33.9 (2)° with respect to each other. The dihedral angles between the mean planes of the sulfonyl-benzene ring and the chloro-pyridine and methyl-pyridine rings are 51.2 (0) and 49.3 (9)°, respectively. The picrate anion inter-acts with the protonated N atom through a bifurcated N-H⋯(O,O) hydrogen bond, forming an R(1) (2)(6) ring motif with the N atom from the methyl-pyridine group of an adjacent cation. N-H⋯O hydrogen bonds, weak C-H⋯O and π-π stacking inter-actions [centroid-centroid distances = 3.8192 (9)and 3.6749 (9)] occur in the crystal packing, creating a two-dimensional network structure along [110].