Na0.44MnO2 has drawn great attention as a promising cathode material for sodium-ion batteries (SIBs) owing to its unique tunnel-type structure that allows facile Na+ insertion/extraction. We here report the controllable preparation of Na0.44MnO2 nanowires (NMO NWs) through electrospinning and annealing processes and their SIB cathode application to boost the ionic diffusion dynamics and cyclic stability. The well-shaped NMO NWs with diameters of 50–200 nm effectively favour the easy access to electrolyte, facilitate the electrons/Na+ ions transportation, and retard the active materials fracture/pulverization upon prolonged cycling. Consequently, fascinating electrochemical performance in terms of high-rate capability (120.4 mAh g−1 at 0.1C; 31.7 mAh g−1 at 50C) and unprecedentedly long cycling life (89% capacity retention after 3300 cycles) is achieved. Furthermore, the underlying Na-ion storage mechanism and migration kinetics have been pioneeringly elucidated by a combination study of ex-situ structure/valence analyses and first-principles computations. The pseudocapacitive behaviour of NMO NWs electrode is also identified to benefit the high-rate performance. Finally, a pouch-type sodium-ion full battery assembled by the NMO NWs cathode and hard carbon nanofibers anode delivers an admirable energy density of 165.3 Wh kg−1 and an outstanding capacity retention of 88.57% over 200 cycles, showing great prospects.