Abstract: The oxygen evolution reaction (OER) represents a critical bottleneck in electrochemical water splitting, and while Fe-based layered double hydroxides (LDHs) exhibit promising catalytic activity, they suffer from severe active species dissolution and sluggish reaction kinetics. A rationally designed Fe₂O₃/FeLa-LDH heterojunction composite was synthesized via a one-step hydrothermal method. Abundant heterointerfaces were created between Fe₂O₃ and FeLa-LDH, which synergistically modulated the local electronic structure and coordination environment. Benefiting from the strong interfacial coupling, the optimized Fe₂O₃/FeLa-LDH electrocatalyst achieves a low overpotential of 366 mV at 10 mA·cm⁻² and outstanding long-term durability with 95% current retention after 100 h. Mechanistic investigations reveal that the heterojunction architecture enhances electrical conductivity, accelerates charge transfer kinetics, and promotes the adsorbate evolution mechanism (AEM) pathway for oxygenated intermediates. This work highlights the pivotal role of heterointerface engineering in overcoming the intrinsic limitations of Fe-based LDHs and provides a facile, scalable strategy for designing high-performance OER electrocatalysts.