Groundwater is a critical resource globally, supporting agriculture, domestic use, and industrial activities, especially in arid and semi-arid locations with inadequate surface water. However, groundwater quality is increasingly deteriorating due to over-extraction, pollution, and saltwater intrusion. The eastern Nile Delta, a region of strategic importance in Egypt for agricultural development, faces significant challenges in groundwater quality management. This study evaluates the groundwater suitability for irrigation purposes in the eastern Nile Delta by conducting a comprehensive hydrogeochemical analysis. Data from 488 groundwater wells and 94 surface water samples were utilized, employing robust methods including Piper diagrams, spatial mapping, and water quality metrics such as sodium adsorption ratio (SAR) and residual sodium carbonate (RSC). The findings indicated that 53.6% of groundwater samples were fresh, 24.3% were brackish, and 22.1% were saline, with fresh water predominantly located in the southern and southwestern regions. Piper diagram analysis identified key water types, including calcium bicarbonate (Ca2⁺−HCO₃−) in fresher zones and sodium chloride (Na⁺−Cl−) in saline-impacted areas. Spatial mapping (mention the type of map/s and the applied method, e.g., weighting criteria analysis in ArcGIS) revealed that approximately 30% of the region was highly suitable for irrigation, while severe restrictions existed in 15–20% of the area, particularly in the north and northeast. These findings provided actionable insights for optimizing irrigation practices and managing water resources effectively. This research offers a replicable framework for similar regions globally, particularly in water-stressed areas facing comparable challenges, enhancing agricultural sustainability.