We report a facile synthesis of new core-Au/shell-CeO2 nanoparticles (Au@CeO2) using a redox-coprecipitation method, where the Au nanoparticles and the nanoporous shell of CeO2 are simultaneously formed in one step. The Au@CeO2 catalyst enables the highly selective semihydrogenation of various alkynes at ambient temperature under additive-free conditions. The core shell structure plays a crucial role in providing the excellent selectivity for alkenes through the selective dissociation of H-2 in a heterolytic manner by maximizing interfacial sites between the core-Au and the shell-CeO2.