The singlet states of cyclopentadienyl (Cp) cations are considered as true prototypes of an antiaromatic system. Due to their high reactivity, their isolation in the solid state as a salt has so far failed. We present here the synthesis of the first room temperature-stable Cp cation salt Cp(C6F5)5Sb3F16 (1·Sb3F16) by single electron oxidation of the corresponding Cp radical Cp(C6F5)5∙ (2) with either an excess of XeF2 and SbF5·SO2 or by hydroxide abstraction from Cp(C6F5)5OH (D) with SbF5·SO2 in hexafluorobenzene. 1·Sb3F16 was characterized by sc-XRD, SQUID, UV-vis, and EPR spectroscopy. Although the aromatic triplet state of the Cp(C6F5)5 cation 1 is energetically favored in the gas phase according to quantum chemical calculations, the coordination of the cation by either Sb3F16⁻ (1a·Sb3F16) or C6F6 (1b·Sb3F16) in the crystal lattice stabilizes the antiaromatic singlet state, which is present in the solid state. The calculated hydride and fluoride ion affinities of 1 are higher than those of the tritylium cation C(C6F5)3+. In addition, results from reactions of 1·Sb3F16 with CO, which most likely yields the corresponding carbonyl complex, and 2 with selected model substrates (Cp2Fe, (Ph3C∙)2, and Cp*Al) are presented.