A new nonlinear optical organic compound, namely, L-histidinium 2-nitrobenzoate (abbreviated as LH2NB (I); ([C(6)H(10)N(3)O(2)](+) [C(7)H(4)NO(4)](-))), was synthesized. The molecular structure of LH2NB (I) was elucidated using single crystal X-ray diffraction technique. The second harmonic generation (SHG) efficiency of this compound is about two times that of the standard potassium dihydrogen phosphate crystals.