The basic structural unit in the title compound, 2,2'-bi(1H-imidazol-3-ium) dichloride, C6H8N42+.2Cl(-), consists of a planar diprotonated biimidazole moiety and two Cl- ions each connected to the dication via a pair of N-H ... Cl bonds. The cation occupies a site of crystallographic 2/m symmetry with the twofold axis running through the connecting C2-C2' bond and the middle of the ring C3-C3' bonds. Contacts of Cl- ions with H atoms in adjacent units generate infinite layers in the (210) planes.