A new synthetic access to the Lewis acid [Au(OTeF(5) )(3) ] and the preparation of the related, unprecedented anion [Au(OTeF(5) )(4) ](-) with inorganic or organic cations starting from commercially available and easy-to-handle gold chlorides are presented. In this first extensive study of the Lewis acidity of a transition-metal teflate complex by using different experimental and quantum chemical methods, [Au(OTeF(5) )(3) ] was classified as a Lewis superacid. The solid-state structure of the triphenylphosphine oxide adduct [Au(OPPh(3) )(OTeF(5) )(3) ] was determined, representing the first structural characterization of an adduct of this highly reactive [Au(OTeF(5) )(3) ]. Therein, the coordination environment around the gold center slightly deviates from the typical square planar geometry. The [Au(OTeF(5) )(4) ](-) anion shows a similar coordination motif.