The first direct observation of pentachlorocyclopentadienyl cation (C5Cl5+) by IR spectroscopy was made in cryogenic SbF5 matrix. The structure of the ion, analyzed by DFT calculations, was found to have D-5h symmetry. It was found that the stabilizing effect of chlorine lone pair electrons, which was observed in other alpha-chlorocarbocations (CCl3+ or C3Cl3+), is not present in this molecule.