4-aminopyridinium hydrogen maleate.

The title compound, C(5)H(7)N(2)(+)...C(4)H(3)O(4)(-), crystallizes in space group P2(1) with one ion pair in the asymmetric unit. The hydrogen maleate anion possesses nearly planar geometry and displays an extremely short intramolecular O--H...O hydrogen bond, with an O...O distance of 2.4198 (19) A. Classical N-H...O hydrogen bonds, together with short C--H...O contacts, generate an extensive hydrogen-bonding network.