Abstract: The sluggish Oxygen Evolution Reaction (OER) remains the primary kinetic bottleneck in Proton-Exchange-Membrane Water Electrolysis (PEMWE). There remains a critical trade-off between activity and stability for currently used noble-metal-based catalysts, and their high cost and scarcity hinder the large-scale application of PEMWEs, thus highlighting the need for high-performance, acid-stable, and low-noble-metal OER catalysts. Herein, a rapid, one-step plasma-assisted fluorination strategy is developed to construct an acid-stable Y-Ru-O pyrochlore catalyst for OER in PEMWEs. Using an O₂ Atmospheric-Pressure Plasma Jet (O₂-APPJ), the precursor film is simultaneously oxidized, fluorinated, and crystallized within minutes. Plasma activation introduced abundant oxygen vacancies and enabled lattice incorporation of fluorine, which modulated the local electronic structure, stabilized Ru oxidation states, and enhanced charge transfer. The resulting catalyst (p-F-YRuO@CC) exhibited a low OER overpotential of 178 mV at 10 mA cm⁻² and outstanding durability, maintaining stable operation for over 70 h in acidic OER and 320 h in a PEMWE. This work demonstrates that plasma-assisted fluorination coupled with pyrochlore defect chemistry provides an efficient route toward durable, high-performance acidic OER anodes.