Electrochemical water splitting is a clean technology that can store the intermittent renewable wind and solar energy in H-2 fuels. However, large-scale H-2 production is greatly hindered by the sluggish oxygen evolution reaction (OER) kinetics at the anode of a water electrolyzer. Although many OER electrocatalysts have been developed to negotiate this difficult reaction, substantial progresses in the design of cheap, robust, and efficient catalysts are still required and have been considered a huge challenge. Herein, we report the simple synthesis and use of alpha-Ni(OH)(2) nanocrystals as a remarkably active and stable OER catalyst in alkaline media. We found the highly nanostructured alpha-Ni(OH)(2) catalyst afforded a current density of 10 mA cm(-2) at a small overpotential of a mere 0.331 V and a small Tafel slope of similar to 42 mV/decade, comparing favorably with the state-of-the-art RuO2 catalyst. This alpha-Ni(OH)(2) catalyst also presents outstanding durability under harsh OER cycling conditions, and its stability is much better than that of RuO2. Additionally, by comparing the performance of alpha-Ni(OH)(2) with two kinds of beta-Ni(OH)(2), all synthesized in the same system, we experimentally demonstrate that alpha-Ni(OH)(2) effects more efficient OER catalysis. These results suggest the possibility for the development of effective and robust OER electrocatalysts by using cheap and easily prepared alpha-Ni(OH)(2) to replace the expensive commercial catalysts such as RuO2 or IrO2.