This work presents two points with respect to manganese oxide (MnO(x)) nanomaterials: their controllable synthesis with desired phases and shapes together with their applications as catalysts for oxygen reduction and Al/air batteries. Solid MnO(x) with crystalline phases of MnOOH, Mn(2)O(3), and MnO(2) as well as shapes of the sphere, wire, rod, and particle were prepared through a simple one-pot hydrothermal route. Selective preparation was achieved by adjusting the surfactant concentration that controls simultaneously the growth thermodynamic and dynamic parameters of MnO(x) nanocrystals. Electrochemical investigations show that the obtained Mn(2)O(3) nanowires, which possess a large aspect ratio and preferentially exposed (222) crystal surfaces, exhibit remarkable catalytic activity (comparable to Pt/C counterparts) toward the electroreduction of oxygen in alkaline media. The tailored MnO(x) nanostructures may find prospective applications as low-cost catalysts for alkaline fuel cells and metal/air batteries.