An unprecedented molecular AuI3 complex has been stabilized in the interlayer space of the Bi2Sr2CaCu2Oy lattice by reacting Au metal with IBi2Sr2CaCu2Oy at 235 degrees C. The stoichiometry of this new intercalate phase is determined as (AuI3)(0.25)Bi2Sr2CaCu2Oy by thermogravimetry and X-ray photoelectron spectroscopy. Micro-Raman and Au L-3-edge extended X-ray absorption fine structure analyses reveal that Au and I are stabilized as the molecular AuI3 (D-3h) in the Bi2Sr2CaCu2Oy lattice with a uniform Au-I bond length of 2.56 Angstrom. According to the powder X-ray diffraction pattern analysis, the basal spacing increases from 15.30 to 18.55 Angstrom with an expansion of 3.25 Angstrom implying that the AuI3 molecules are intercalated into the [Bi-O] double layers with a parallel geometry. The present AuI3 entity is the first of the three coordinated molecular Au-complexes to be stabilized in a solid matrix at room temperature.