For the first time, HH dissociation on an unsupported nanoporous gold (AuNPore) surface is reported for chemoselective hydrogenation of C C, C=C, C=N, and C=O bonds under mild conditions (8 atm H2 pressure, 90 degrees C). Silver doping in AuNPore, which was inevitable for its preparation through a process of dealloying of AuAg alloy, exhibited a remarkable difference in catalytic activity between two catalysts, Au(> 99)Ag(1)NPore and Au(90)Ag(10)NPore.The former was more active and the latter less active in H-2 hydrogenation, while the reverse tendency was observed for O-2 oxidation. This marked contrast between H-2 reduction and O-2 oxidation is discussed. Further, Au(> 99)Ag(1)NPore showed a high chemoselectivity toward reduction of terminal alkynes in the presence of internal alkynes which was not achieved using supported gold nanoparticle catalysts and other previously known methods. Reductive amination, which has great significance in synthesis of amines due to its atom-economical nature, was also realized using Au(> 99)Ag(1)NPore, and the Au(> 99)Ag(1)NPore/H-2 system showed a preference for the reduction of aldehydes in the presence of imines. In addition to this high chemoselectivity, easy recovery and high reusability of AuNPore make it a promising heterogeneous catalyst for hydrogenation reactions