Global Mercury Observation System confirms that most of the mercury emissions and re-emissions emerge from South Asia. However, there is a lack of human health risk assessment based on mercury in this region which is crucial to identify hotspots, develop management strategies and to estimate the total population at risk. In this study, we present the human health risk map from the exposure to mercury contamination in drinking groundwater by using the probability kriging geostatistical method for Lucknow monitoring area (1222 Km2) which is situated in the central part of the Ganga Alluvial Plain, Northern India. Our human health risk map contributes to the identification of potential hotspots across all the three distinct sectors (urban, rural and combined farming) of this diverse region. We have compiled mercury data in our previous published study and here, we confirm that the health of the significant population of the region is at risk due to the regular intake of mercury-contaminated drinking water. The dissolved mercury concentrations ranges from 9.74 to 61.42 ppb with an average value of 15.38 ppb. Risk quotients were computed by comparing exposure concentrations with the World Health Organization guideline value (1.0 ppb) to. Additionally, we have also identified the fraction of monitoring area at risk and estimated the health of total inhabitants risk areas through a spatial overlay of the risk map with the area and population data. We have discovered that the probability of exceedance of mercury is the highest in the combined farming sector of the monitoring area due to the presence of various anthropogenic interferences. In the urban sector, the hotspot with high to very high probability for health risk is located in the highest population density regions, where 32% of the total population resides in the 7% of the total land of the monitoring area. In Northern India, these potential hotspots are in the Ganga Alluvial Plain that provides drinking water resources to its habitants who account for ~7% of the world population. Overall, we suggest that the risk from mercury exposure should be considered as a priority by environmental risk managers as it is affecting one of the most densely-populated and agriculturally-productive regions of the South Asia.