Development of efficient and affordable electrocatalysts towards water oxidation is important for the large-scale production of hydrogen. Herein, for the first time, we report a two-dimensional (2D) ultrathin NiTe nanosheets as a highly effective catalyst for electrochemical oxygen evolution reaction (OER) via a facile one-pot in-situ hydrothermal approach by using three-dimensional (3D) nickel foam (NF) as both catalyst support and source of nickel. The morphology, electrochemical active surface area (ECSA) and the catalytic activity can be easily engineered by the reaction conditions. The prepared 2D NiTe ultrathin nanosheets have large number of exposed active sites and 3D hierarchical porous structure, which offer superior activity for water oxidation. The electrode only needs an overpotential of 410 mV to afford an extraordinarily high current density of 300 mA cm - 2 and exhibits excellent long-term water catalysis durability. This facile approach for preparation of highly active ultrathin NiTe catalyst is novel and applicable to a wide range of functional materials for various applications including catalysis, energy conversion and energy storage.