The development of Serang City as the central government of Banten Province leads to persistently increasing demand for clean water in the area and its surroundings. This study aimed to perform the hydrogeological mapping of the southwestern part of Serang Regency. The study area covered four districts, namely Baros, Padarincang, Paburuan, and Ciomas. These four districts are the clean water source of Serang City that also functions as a buffer zone designed for the development of freshwater fishery and wetland agriculture. Hydrogeological mapping in the study area is expected to be one of the inputs in planning the use of water resources. The method used in this research included analyses of drill data, geophysical measurement results, the findings of previous studies, hydrological map scale 1:250000, and geological map scale 1:100000, as well as geomorphological mapping and field survey. This research produced six classes of hydrogeological units that covered areas with scarce groundwater productivity up to those with high groundwater productivity.