In this study an electrochemical approach is proposed for the fabrication of nanoporous gold (NPG)-supported manganese oxide nanowires. This method consists in: (i) electrodepositing an Au–Mn alloy, (ii) selectively corroding Mn under electrochemical control, forming simultaneously the NPG support and the functional Mn-oxide decorating the nanopores. The electrodeposition process is carried out from a bath based on eutectic urea/choline chloride ionic liquid. The electrochemical dealloying/oxidation step is performed in an aqueous solution. The oxidation process, performed by cyclic voltammetry (CV) in aqueous solution, has been monitored in situ by visible reflectivity measurements. The crystal structure and the morphology of the electrodeposited Au–Mn alloy have been examined by XRD and SEM, respectively. The 3D morphology of the nanostructure has been characterised by FIB/FEG-SEM. The specific capacity of NPG-supported nanostructured Mn-oxide has been measured by CV and found to be notably better than that of unsupported electrodeposited Mn-oxide nanowires.