Alkaline water electrolysis yielding H2 and O2 is a very promising fuel cell technology for sustainable energy generation. Emphasis has been placed on the development of efficient electrocatalysts based on earth-abundant elements for the kinetically deterred oxygen evolution reaction (OER). Nickel boride nanostructures exhibit enhanced OER catalytic activity, achieving 10 mA cm-2 at an overpotential of 320 mV. The activity can be greatly improved by incorporating Ni3B in an electrically conducting reduced graphene oxide matrix, which reduces the overpotential further to 290 mV at 10 mA cm-2, and has a small Tafel slope. The catalytic activity of the Ni3B-rGO nanocomposite shows considerable stability under long-term operating conditions.