Herein, we report an effective carbon encapsulation strategy to boost the capacitive performance of WO_3−x nanowires as a high-energy and stable anode material for flexible asymmetric supercapacitors (ASCs). The carbon-encapsulated WO_3−x nanowires exhibited a remarkable areal capacitance of 786.8 mF cm⁻² and excellent durability. Furthermore, an ASC device with high energy and power density was also fabricated from the as-prepared carbon encapsulated WO_3−x nanowire anode.