In the title compound, C(3)H(5)N(2) (+)·C(4)H(3)O(4) (-), the dihedral angle between the imidazolium ring and the plane formed by the fumarate anion is 80.98 (6)°. In the crystal structure, inter-molecular O-H⋯O and N-H⋯O hydrogen bonds form extended chains along [100] and [01], creating a two-dimensional network.