The crystal structure of the title salt, C12H9N2 (+)·HSO4 (-)·H2O, comprises inversion-related pairs of phenazinium ions linked by C-H⋯N hydrogen bonds. The phenazinium N-H atoms are hydrogen bonded to the bis-ulfate anions. The bis-ulfate anions and water mol-ecules are linked by O-H⋯O hydrogen-bonding inter-actions into a structural ladder motif parallel to the a axis.