<p>A highly sensitive and selective poly(vinyl chloride) (PVC) membrane sensor for the potentiometric determination of Pb²⁺ ions was developed using 3-hydroxy-4-[(2-hydroxy-5-methylphenyl)azo]-1-naphthalenesulfonic acid as an ionophore. The sensor exhibited a Nernstian response with a slope of 29.25 ± 0.82&#xa0;mV/decade over a wide linear concentration range of 1.0 × 10^–5–1.0 × 10^–1&#xa0;M (<i>R</i>² = 0.9998) and a low detection limit of 4.35 × 10^–6&#xa0;M, demonstrating high sensitivity. The newly developed sensor exhibited excellent repeatability and high selectivity against a wide range of potentially interfering ions, including alkali and alkaline earth metals. The sensor had a rapid response time of less than 10&#xa0;s and a wide operational pH range of 5.0–9.0. Its applicability was successfully demonstrated for the determination of Pb²⁺ in environmental water samples, yielding recoveries greater than 95.5%. Overall, the fabricated sensor offers a simple, low cost, rapid, and reliable approach for the selective potentiometric detection of Pb²⁺ ions.</p> Graphical abstract <p></p>