The swelling potential of fine-grained soils is a critical factor influencing the engineering and agricultural design of foundations, as it can cause significant expansion-related issues. This study investigates the swelling potential of clayey soils in the southern region of Urmia Lake, located in East Azerbaijan Province, NW Iran. A comprehensive set of laboratory tests was conducted on 125 soil samples collected from 25 distinct locations. The analyses included assessments of physicochemical properties, soil classification according to the USDA system, and clay mineralogical composition. Regression analysis was employed to develop predictive formulas for swelling potential based on laboratory indices, including water absorption, porosity, density, specific gravity (Gs), sulfate (SO4-) and chloride (Cl-) concentrations, pH, Casagrande limits, unconfined compressive strength (UCS), X-ray diffraction (XRD) patterns, and clay content. The results revealed that the studied soils, classified as clay, clay loam, and silty clay, exhibit swelling potentials ranging from moderate to high. This research provides valuable insights for designing stable structures and optimizing land use in the region.