This study aimed to evaluate the quality of groundwater used in 19 mosques and Quranic centers within the municipality of Tajoura. A total of 38 water samples were collected and subjected to physical, chemical, and microbiological analyses. The results revealed a significant variation in water characteristics. While pH values remained within the permissible range (6.89–7.76), other indicators showed record-high levels exceeding approved standards. Electrical Conductivity (EC) reached a peak of 12,540 μS/cm, and Total Dissolved Solids (TDS) ranged between 478 and 7,800 mg/L. Furthermore, the study identified critical levels of Total Hardness (TH), peaking at 2,362 mg/L in the Musa bin Nusayr Mosque. Regarding ionic concentrations, elevated levels of Sodium, Potassium, Bicarbonate, and Calcium were recorded in several locations, indicating seawater intrusion and the impact of human activities. Microbiological testing revealed bacterial contamination in multiple sites, with 26.31% of the samples testing positive for Escherichia coli (E. coli). This confirms direct fecal contamination, rendering the water unfit for human consumption according to World Health Organization (WHO) standards. The study concludes with an urgent recommendation for immediate intervention to address pollution sources and implement disinfection systems to protect worshippers and students.............. Keywords:............Groundwater Quality, Tajoura Municipality, Bacterial Contamination, Seawater Intrusion, Escherichia coli.