Ammonia (NH₃) is considered an important chemical for both agriculture fertilizer and renewable energy. The conventional Haber-Bosh process to produce NH₃ is energy intensive and leads to significant CO₂ emission. Alternatively, electrochemical synthesis of ammonia (ESA) through the nitrogen reduction reaction (NRR) by using renewable electricity has recently attracted significant attention. Herein, we report a metal-organic framework-derived nitrogen-doped nanoporous carbon as electrocatalysts for the NRR. It exhibits a remarkable production rate of NH₃ up to 3.4×10⁻⁶ mol cm⁻² h⁻¹ with a Faradaic efficiency (FE) of 10.2% at −0.3 V vs RHE under room temperature and ambient pressure using aqueous 0.1 M KOH electrolyte. Increasing the temperature to 60 °C was found to further improve production rates to 7.3×10⁻⁶ mol cm⁻² h⁻¹. The stability of the nitrogen-doped electrocatalyst was demonstrated during an 18-hour continuous test with constant production rates. First principles calculations were used to elucidate the possible active sites and reaction pathway. The moiety, which consists of three pyridinic N atoms adjacent with one carbon vacancy embedded in a carbon layer, is able to strongly adsorb N₂ and further realize N≡N triple bond dissociation for the subsequent protonation process. The rate-determining step of the NRR is predicted to be the adsorption and bond activation of the N₂ molecule. Increasing overpotentials are favorable for the protonation process during NH₃ generation. Further doping Fe into the nitrogen-doped carbon likely blocks the N₃ active sites and facilitates the hydrogen evolution reaction, a strong competitor to the NRR, thus yielding negative effect on ammonia production. This work provides a new insight into the rational design and synthesis of nitrogen-doped and defect-rich carbon as efficient NRR catalysts for NH₃ synthesis at ambient conditions.