<p>This study provides a hydrogeochemical characterization and quality assessment of groundwater in the coastal aquifers of Puri District, Odisha, India. Owing to rapid urbanization and proximity to the Bay of Bengal, understanding groundwater chemistry is critical for evaluating its suitability for domestic and agricultural use. A total of 80 groundwater samples collected across four seasons were analyzed for major ions and physicochemical parameters. The ionic abundance followed the order of Na⁺  &gt; Ca²⁺  &gt; Mg²⁺  &gt; K⁺ for cations and Cl⁻  &gt; HCO &gt; SO &gt; NO for anions. Hydrochemical facies, interpreted through Piper tri-linear diagrams, indicate a seasonal transition from fresh Ca–HCO₃ types during the monsoon to mixed Ca–Mg–Cl and Na–Cl types during pre-monsoon and winter seasons, revealing active cation exchange and localized salinization. The Gibbs diagram demonstrates that rock weathering is the principal mechanism governing baseline mineralization for 90% of the samples, while 10% are driven by evaporative concentration. Thermodynamic modelling revealed consistent super-saturation for Calcite (SI =  + 0.068 to + 0.524), whereas significant under-saturation of Halite (SI &lt;  − 6.5) and Gypsum (SI &lt;  − 2.2) indicated that evaporite dissolution is not the primary source of salinity. Together with Na⁺/Cl⁻ ratios and chloride-dominant hydrochemical facies, these results suggest possible saline-water mixing within the coastal aquifer system. Multivariate statistical analysis using Principal Component Analysis (PCA) in IBM-SPSS extracted three principal components explaining over 91% of the total cumulative variance, successfully isolating geogenic mineral dissolution from anthropogenic nitrate enrichment (PC3 loading = 0.92). Water Quality Index (WQI) evaluation showed that 58–83% of groundwater samples were classified as excellent to good for drinking purposes, while irrigation indices, particularly SAR, indicated that 74–92% of samples were suitable for agricultural use, with localized quality deterioration observed in a few coastal blocks. This integrated thermodynamic and statistical approach provides a quantifiable, diagnostic framework for groundwater pathways, supporting targeted, sustainable water resource management in vulnerable coastal zones in alignment with Sustainable Development Goal (SDG) 6.</p>