In the title molecular salt, C(7)H(14)N(5)O(+)·Cl(-) (the HCl salt of the oxo derivative of the triazine herbicide simazine), the cation and anion are linked by N-H⋯Cl hydrogen bonds. The chloride ion is also involved in a close electrostatic inter-action with an inversion-related triazine ring [Cl⋯centroid distance = 3.201 (1) Å]. A π-π inter-action having a centroid⋯centroid distance of 3.456 (2) Å exists between pairs of rings via another inversion relation. The triazine ring and adjacent non-H atoms are essentially planar (r.m.s. deviation = 0.042 Å), while both methyl groups are approximately perpendicular and on the same side of the plane [torsion angles = 79.3 (3) and -84.6 (3)°]. Upon exposure to X-rays for about two days, the color of the title compound changed from colorless to a pale yellow-orange with no apparent affect on the structure as evidenced by no significant change in the intensities of the standard reflections.