A novel triiodide phase of the formamidinium cation, CH5N2+.I3-, crystallizes in the triclinic space group P1 at a temperature of 110 K. The structure consists of two independent isolated triiodide ions located on inversion centers. The centrosymmetric character of I3- was additionally confirmed by the observed pronounced peaks of symmetrical oscillations of I3- at 115-116 cm-1 in Raman scattering spectra. An additional structural feature is that each terminal iodine atom is connected with three neighboring planar formamidinium cations by N-H···I hydrogen bonding with the N-H···I bond length varying from 2.81 to 3.08 A °, forming a deformed two-dimensional framework of hydrogen bonds. A Mulliken population analysis showed that the calculated charges of hydrogen atoms correlate well with hydrogen-bond lengths. The crystal studied was refined as a three-component twin with domain ratios of 0.631 (1):0.211 (1): 0.158 (1).