<p>Oxolinic acid, a first-generation quinolone antibiotic, has been widely used in veterinary medicine and aquaculture for the prevention and treatment of bacterial infections. Its persistence in the environment, primarily due to incomplete removal by conventional wastewater treatment, raised concerns about antibiotic resistance and environmental contamination. This study explored the electrochemical degradation of oxolinic acid (10&#xa0;µM) in both simulated and real seawater using boron-doped diamond electrodes (9 cm²) under galvanostatic conditions. Various supporting electrolytes–NaBr, NaCl, Na₂SO₄, Na₂CO₃, NaHCO₃, and Na₂B₄O₇·10H₂O–were tested to evaluate the influence of typical seawater constituents on degradation efficiency. Results showed degradation ranging from 50 to 99% after 2&#xa0;h, with NaBr delivering the highest performance, achieving over 90% degradation even at a low current density of 1.1&#xa0;mA&#xa0;cm⁻². The addition of other salts to NaBr solutions maintained high degradation levels while improving energy efficiency. Degradation rates were largely independent of current density, although slightly enhanced at higher currents, at the expense of increased energy consumption. In real seawater, oxolinic acid was nearly completely removed (&gt; 99%) at 1.1&#xa0;mA&#xa0;cm⁻², with energy consumption as low as 0.13&#xa0;kJ&#xa0;kg⁻¹. These findings demonstrated the potential of electrochemical oxidation using boron-doped diamond electrodes as an effective and energy-efficient strategy for removing oxolinic acid from saline wastewaters, contributing to the mitigation of antibiotic contamination in aquatic environments.</p> Graphical Abstract <p></p>