(E)-2-[4-(Diethyl-amino)-styr-yl]-1-methyl-pyridinium 4-meth-oxy-benzene-sulfonate monohydrate.

In the cation of the title compound, C(18)H(23)N(2) (+)·C(7)H(7)O(4)S(-)·H(2)O, one ethyl group of the diethyl-amino unit is disordered over two sets of sites in a 0.665 (6):0.335 (6) ratio. The styrylpyridinium unit is nearly planar, with a dihedral angle between the pyridinium and benzene rings of 4.27 (8)°. In the crystal, the anion ring is almost perpendicular to the aromatic rings of the cation; the sulfonate-substituted benzene ring forms dihedral angles of 89.60 (8) and 89.37 (8)°, respectively, with the pyridinium and benzene rings of the cation. In the crystal, the three components are linked into a three-dimensional network by O-H⋯O and C-H⋯O hydrogen bonds. π-π inter-actions with centroid-centroid distances of 3.6999 (9) and 3.7106 (9) Å are also present.