Abstract Designing catalysts that can simultaneously accelerate reactant activation and hydrogenation remains a central challenge in electrochemical ammonia synthesis. Here, a computation‐guided, dual‐site electrocatalyst design strategy that bridges first‐principles theory with device‐level validation is reported. Guided by density functional theory, Cu‐doped ZnO is identified as an optimal dual‐site platform: Cu sites upshift the Zn d‐band center, strengthening * NO 2 adsorption and enabling facile deoxygenation, while ZnO sites promote water dissociation to supply protons at the reaction interface. This cooperative synergy precisely tunes nitrite activation and hydrogenation kinetics, suppressing competing hydrogen evolution. The resulting catalyst achieves a record NH 3 yield of 552.16 mg h −1 cm −2 with 87.9% Faradaic efficiency in a membrane electrode assembly—4× and 18× higher than flow‐ and H‐cell configurations, respectively. Operando spectroscopy confirms the predicted mechanism, demonstrating a theory‐to‐device workflow that replaces trial‐and‐error with predictive catalyst design. This approach establishes a generalizable paradigm for developing advanced electrocatalysts for sustainable chemical transformations.