Atomically monodisperse Au-25(SR)(18) (where R=-CH2CH2Ph) nanoparticles are explored as a stereoselective catalyst for hydrogenation of cyclic ketone to one specific isomer of cyclic alcohol product. A complete (similar to 100%) stereoselectivity is obtained. The catalytic performance is correlated with the crystal structure and core-shell electronic nature of Au-25(SR)(18) superatoms, in which the electron-rich Au-13 core activates the C=O bond, whereas the electron-deficient Au-12 shell provides active sites for H-2 adsorption and dissociation. This work demonstrates promising catalytic performance of ultrasmall gold nanoparticles. The atomically precise Au-25(SR)(18) superatom catalyst may be explored as hydrogenation catalysts for some important chemical processes. (C) 2010 Elsevier Inc. All rights reserved.