Vertically aligned Ni(OH) nanosheets were grown on carbon paper (CP) current collectors through a simple and cost-effective hydrothermal approach. The as-grown nanosheets are porous and highly crystallized. If used as a monolithic electrode for electrochemical water oxidation in alkaline solution, the carbon paper supported Ni(OH) nanosheets [CP@Ni(OH) ] exhibit high electrocatalytic activity and excellent long-term stability. The electrode can attain an anodic current density of 20 mA cm at a low overpotential of 338 mV, comparable to that of state-of-the-art RuO nanocatalysts supported on CP (CP/RuO ) with the same catalyst loading. Significantly, CP@Ni(OH) shows much better long-term stability than CP/RuO upon continuous galvanostatic electrolysis, particularly at a high industry-relevant current density such as 100 mA cm . CP@Ni(OH) can sustain water oxidation at 100 mA cm for 50 h without any degradation, whereas the performance of CP/RuO is much poorer and deteriorates gradually over time. CP@Ni(OH) electrodes hold substantial promise for use as low-costing water oxidation anodes in electrolyzers.