Metal oxides such as manganese dioxide (MnO2) are often used as electrode materials for supercapacitors due to their high specific capacitance. In practice, however, their specific capacitance is much smaller than the theoretical limit due to the low electrical conductivity and serious agglomeration. In the present work, we demonstrate that highly conductive nanoporous silver (NPS) network with uniform continuous nanoporosity and high surface area which was fabricated by dealloying Ag-Mg-Ca metallic glasses can be employed as supports and collectors for MnO2 capacitors. By plating the MnO2 nanocrystals into the nanopore structure, the NPS/MnO2 composite electrode provides fast ionic conduction and excellent electron-proton transport, resulting in an ultrahigh specific capacitance of the plated active MnO2 (similar to 1088 F g(-1)), which is close to the theoretical limit. The unique combination of high specific capacitance and long cycle life enhanced by the current composite structure makes the NPS/MnO2 composite promising for electrochemical supercapacitor as electrode material. In addition, our findings suggest that the uniform NPS network is capable for improving capacitance performance of metal oxides in electrochemical supercapacitors. (C) 2015 Elsevier Ltd. All rights reserved.