We prepared single, crystalline, Na4Mn9O18 nanowires with a polymer-pyrolysis method using polyacrylates of Na and Mn as precursor compounds. The optimized Na4Mn9O18 materials display high crystallinity and a homogeneous nanowire structure, which provides a mechanically stable structure as well as a short diffusion path for Na-ion intercalation and extraction. The Na4Mn9O18 nanowires have shown a high reversible capacity (128 mA h g-1 at 0.1C), excellent cycleability (77% capacity retention for 1000 cycles at 0.5C), and promising rate capability for Na-ion battery applications. The outstanding performance of the Na4Mn9O18 nanowires makes them a promising candidate to construct a viable and low-cost Na-ion battery system for upcoming power and energy storage systems.