The asymmetric unit of the title salt, [p-FC6H4CH2NH3]+⋅H2PO4-, contains one 4-fluorobenzylammonium cation and one dihydrogen phosphate anion. In the crystal, the H2PO4- anions are linked by O--H⋯O hydrogen bonds to build corrugated layers extending parallel to the ab plane. The FC6H4CH2NH3+ cations lie between these anionic layers to maximize the electrostatic interactions and are linked to the H2PO4- anions through N--H⋯O hydrogen bonds, forming a three-dimensional supramolecular network. Two hydrogen atoms belonging to the dihydrogen phosphate anion are statistically occupied due to disorder along the OH⋯HO direction. [ABSTRACT FROM AUTHOR]