We present the combined experimental and theoretical investigations of optical properties and excitation energies of metallic iridium. The reflected energy loss spectroscopy (REELS) spectra of polycrystalline Ir were measured with a cylindrical mirror analyzer in UHV conditions at primary energies of 500, 1000 and 2000 eV. The energy loss function (ELF) and thereby the refractive index n and the extinction coefficient k were calculated from these REELS spectra in the loss energy range of 2-200 eV by applying our reverse Monte Carlo method. The high accuracy of the obtained results is justified with the ps- and f-sum rules. Using the derived ELF the inelastic mean free paths of Ir were calculated from 1 eV up to 10 keV. Moreover, we identified for the first time in the optical data the 5p(3/2), 4f(5/2) and 4f(7/2) shell excitations of the solid Ir sample.