Developing oxygen evolution reaction (OER) electrocatalysts that can operate at industrial current densities with high activity and long-term stability represents a key challenge for the practical implementation of anion exchange membrane water electrolysis (AEMWE). Herein, we report an Ir–Ni dual-site catalyst constructed via anion-coordination modulation, comprising Ir single atoms anchored on N-doped ultrathin NiO nanosheets on nickel foam (Ir-NiNO/NF) for alkaline OER. The N doping induces charge redistribution, lowers the Ir oxidation state, and optimizes the electronic environment via Ir–N coordination. In-situ Raman measurements reveal that the N doping effectively lowers the formation potential of the NiOOH active species and promotes interfacial charge transfer. Density functional theory calculations combined with in-situ differential electrochemical mass spectrometry (DEMS) confirm an oxide pathway mechanism (OPM) on Ir–Ni dual sites, bypassing scaling limitations of the conventional adsorbate evolution mechanism and structural degradation of the lattice oxygen mechanism. The self-supported electrode achieves ultralow overpotentials of 209 and 363 mV at 10 and 500 mA·cm⁻². An AEMWE electrolyzer using Ir-NiNO/NF as both diffusion layer and anode requires 1.7 V at 2 A·cm⁻² (60 °C) and operates stably for > 280 h at 1 A·cm⁻². This study provides new insights into low-Ir-loading, high-activity OER catalyst design and dual-site catalytic mechanisms.