The new compound (CH3NH3)(3)Tl2Cl9 was synthesized and fully characterized. X-ray photoelectron spectroscopy and Raman spectroscopy are consistent with the crystal structure solved by single-crystal X-ray diffraction. This compound is a semiconductor with a measured band gap of E-g = 2.91 eV. It is the first thallium-based hybrid perovskite and shows remarkably high stability to ambient conditions.