l-Prolinamidium hydrogensquarate.

Cations of the title compound, C5H11N2O+·C4HO4−, are connected by inter­molecular N(amide)— H⋯O(amide) hydrogen bonds into helical chains, whereas anions are inter­linked by strong O(hydrox­yl)—H⋯O hydrogen bonds into chains. These two distinct chains are interconnected by both N(amide)—H⋯O and N(ammonium)—H⋯O hydrogen bonds into a three-dimensional framework. One of the ammonium protons is involved in a three-centre hydrogen bond. [ABSTRACT FROM AUTHOR]