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The increased interest in smart and portable electronic gadgets has led to the development of flexible and wearable energy storage systems. Herein, the oxygen vacancy-enriched Na-MnO2-xis synthesized using a simple, scalable, and inexpensive electrodeposition method. The oxygen vacancy enrichment effectively enhances the conductivity and reaction kinetics of the Na-MnO2electrode. The Na-MnO2-xfilm electrode reveals an excellent specific capacitance of 395 F g−1at the scan rate of 5 mV s−1with high capacitance retention of 85.9 % after 10,000 cycles at a current density of 5 A g−1. To verify the practicability, three asymmetric supercapacitors (ASCs) (Mn3O4//Ti3C2Tx, Na-MnO2//Ti3C2Tx, and Na-MnO2-x//Ti3C2Tx) are fabricated and their respective performances are contrasted. The Na-MnO2-x//Ti3C2TxASC reveals a maximum energy density of 25 Wh kg−1at the power density of 1000 W kg−1, along with excellent capacitance retention of 98.8 % after 10,000 cycles. In addition, to validate the suitability of Na-MnO2-xelectrode for flexible energy storage, the flexible Na-MnO2-x//Ti3C2TxASC is fabricated that operates in the potential window of 2 V in PVA: Na2SO4polymer gel electrolyte and delivers a high volumetric energy density of 510.3 mWh cm−3at a power density of 40,483 mW cm−3. Moreover, the electrocatalytic activity of Na-MnO2-xthin films reveals an overpotential of 439.7 and 381.2 mV to drive a current density of 10 mA cm−2corresponding to HER and OER, respectively. Therefore, the electrodeposited, oxygen vacancy-enriched Na-MnO2-xfilm electrode has great potential to be used for both flexible energy storage and electrocatalysis.