The title compound, 2C₁₄H₁₃N₂⁺·S₂O₈^2-·2H₂O, is a protonated amine salt which is formed from two rather uncommon ionic species, namely a peroxodisulfate (pds^2-) anion, which lies across a crystallographic inversion centre, and a 2,9-dimethyl-1,10-phenanthrolin-1-ium (Hdmph⁺) cation lying in a general position. Each pds^2- anion binds to two water molecules through strong water-peroxo O–H⋯O interactions, giving rise to an unprecedented planar network of hydrogen-bonded macrocycles which run parallel to (100). The atoms of the large R₈⁸(30) rings are provided by four water molecules bridging in fully extended form (⋯H–O–H⋯) and four pds^2- anions alternately acting as long (⋯O–S–O–O–S–O⋯) and short (⋯O–S–O⋯) bridges. The Hdmph⁺ cations, in turn, bind to these units through hydrogen bonds involving their protonated N atoms. In addition, the crystal structure also contains π–π and aromatic-peroxo C–H⋯O interactions.