Ambient electroreduction of nitrogen (N₂) is considered as a green and feasible approach for ammonia (NH₃) synthesis, which urgently demands for efficient electrocatalyst. Morphology has close relationship with catalytic activity of heterogeneous catalysts. Nanoribbon is attractive nanostructure, which possesses the flexibility of one-dimensional nanomaterials, the large surface area of two-dimensional nanomaterials, and lateral size confinement effects. In this work, Cu₃P nanoribbon is proposed as a highly efficient electrocatalyst for N₂-to-NH₃ conversion under benign conditions. When measured in N₂-saturated 0.1 M HCl, such Cu₃P nanoribbon achieves high performance with an excellent Faradaic efficiency as high as 37.8% and a large yield of 18.9 µg·h⁻¹·mg_cat.⁻¹ at −0.2 V. It also demonstrates outstanding stability in long-term electrolysis test at least for 45 h.