The high-activity of metallic nanofilament array (NFA) embedded tungsten oxide (WO 3 ) bifunctional electrodes for electrochromism and electrochemical energy storage is presented. The NFA reduces charge transfer resistance and increases the electrochemically active surface area at the electrode-electrolyte interface. The NFA-embedded WO 3 electrode exhibits a specific capacity of 214 F g −1 (pristine WO 3 : 133 F g −1 ) at 0.25 mA cm −2 , excellent cycling stability with ∼92% capacitance retention after 2000 cycles (pristine WO 3 : ∼75% capacitance retention) and a coloration efficiency of 128 cm 2 C −1 (pristine WO 3 : 91 cm 2 C −1 ) with superb optical modulation. These properties are significantly more advanced compared to the pristine WO 3 electrode and superior to previously reported WO 3 -based composites and nanostructured materials. Nanofilament array embedded metal oxide for a highly efficient electrochemical electrode.