Abstarct: In this study, a new azo ligand, 1-{3-[(3-hydroxypropylamino)methyl]-4-hydroxyphenylazo}-4-chloro-3-nitrobenzene L2, was used as a colorimetric sensor for the selective detection of cyanide ions. The ligand L2 was characterized and investigated using several different spectroscopic techniques to confirm its chemical structure and properties. The sensing behavior toward a series of different anions was studied using UV–Vis spectroscopy. Upon the addition of cyanide ions, the sensor exhibited a clear and rapid color change from yellow to orange, whereas no significant response was observed toward other interfering anions, indicating the high selectivity of the sensor toward cyanide ions. In addition, the changes occurring in the absorption spectra after the addition of cyanide ions were investigated, and the results indicated the formation of a stable complex between the ligand and the cyanide ion. The binding stoichiometry between the ligand and the cyanide ion was determined using Job’s plot, and the results showed a 1:1 interaction ratio. Furthermore, the limit of detection (LOD) and the limit of quantification (LOQ) were found to be 7/34 × 10⁻6 M and 2/44 × 10⁻5 M, respectively, indicating the suitable sensitivity of the sensor for cyanide ion detection. The effect of time on the performance and stability of the sensor was also investigated over different time intervals, and the results confirmed the good stability and reproducibility of the sensing response. baxsed on the experimental results and previous studies, a possible sensing mechanism was proposed, which is likely to occur through the formation of hydrogen bonds and electronic changes in the ligand structure after the addition of cyanide ions. The final results demonstrated that the synthesized ligand can be used as an efficient, simple, rapid, and selective colorimetric sensor for the detection of cyanide ions in solutions and has potential applications in environmental and analytical fields.