Abstract: Electrocatalytic N₂ reduction reaction (NRR) has been considered as a promising and alternative strategy for the synthesis of NH₃, which will contribute to the goal of carbon neutrality and sustainability. However, this process often suffers from the barrier for N₂ activation and competitive reactions, resulting in poor NH₃ yield and low Faraday efficiency (FE). Here, we report a two-dimensional (2D) ultrathin FeS nanosheets with high conductivity through a facile and scalable method under mild condition. The synthesized FeS catalysts can be used as the work electrode in the electrochemical NRR cell with N₂-saturated Na₂SO₄ electrolyte. Such a catalyst shows a NH₃ yield of 9.0 μg·h⁻¹·mg⁻¹ (corresponding to 1.47 × 10⁻⁴ μmol·s⁻¹·cm⁻²) and a high FE of 12.4%, which significantly outperformed the other most NRR catalysts. The high catalytic performance of FeS can be attributed to the 2D mackinawite structure, which provides a new insight to explore low-cost and high-performance Fe-based electrocatalysts, as well as accelerates the practical application of the NRR.