In this study, manganese oxide (MnOx)-decorated carbonized porous silicon nanowire arrays (MnOx/C/PSiNWs) are synthesized through eco-friendly and cost-effective processes. This electrode material system exhibits excellent electrochemical behavior with a specific capacitance reaching 635 F g(-1), as well as the highest areal power (100 mWcm(-2)) and energy (0.46 mW h cm(-2)) ever reported in a silicon nanowire-based pseudocapacitor electrode. Furthermore, an asymmetric hybrid supercapacitor (AHS) is designed using MnOx/C/PSiNWs as the positive electrode, carbonized porous silicon nanowires (C/PSiNWs) as the negative electrode and 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI)/acetonitrile as the electrolyte. The supercapacitor shows an excellent power density of 25 kW kg(-1) and an energy density of 261 W h kg(-1) at a current density of 0.2 mA cm(-2) with a large operational potential window (3.6 V) and a good capacitance retention (82% after 10 000 CV cycles). The results show that the MnOx/C/PSiNW electrodes are promising materials for the future generation of high performance supercapacitors.