Abstract <p>The need for clean water in coastal areas is threatened due to the potential increase in groundwater salinity. The purpose of this study was to study the level of groundwater salinity and mixing of seawater with groundwater based on chloride content in the South Coast of Jember. This study used a quantitative descriptive survey method by observing 65 samples spread in the South Coastal region of Jember, with a focus on analyzing 11 samples to determine chloride content, in addition to one seawater sample taken to determine the seawater fraction. The seawater fraction was calculated using the mixing ratio equation. Primary data includes EC (Electrical Conductivity), TDS (Total Dissolved Solids), and temperature, and chemical parameters in the form of chloride ions. Spatial mapping was conducted using the geostatistical method of the Ordinary Kriging model. The results on the classification of groundwater salinity based on chloride content show that 27% of the 11 samples can be categorized as fresh water, 45% as slightly saline groundwater, 9% as highly saline groundwater, and 18% as very highly saline groundwater. The most dominant classification of groundwater salinity based on chloride content is slightly saline groundwater. The highest level of mixing of seawater with groundwater identified using the chloride element has a percentage of 23.4% at point SG-55 and 10.6% at point SG-56 which occurs in Sumberejo Village. This suggests that there is seawater contamination in the groundwater indicating salinity caused by exploitation of groundwater that is more dominant than in other areas.</p>