In the title compound, guanidinium chloridotrioxidochrom­ate(VI), (CH₆N₃)[CrClO₃], both the cation and anion are generated by crystallographic mirror symmetry, with one O and one N atom and the Cr, Cl and C atoms lying on the mirror plane. The bond lengths in the guanidinium cation are inter­mediate between normal C—N and C=N bond lengths, indicating significant delocalization in this species. In the crystal structure, inter­molecular N—HCl inter­actions generate R₂¹(6) ring motifs. These ring motifs are further inter­connected by inter­molecular N—HO hydrogen bonds into infinite chains along [010].