Ground-Water Microbiology and Geochemistry is a work designed to bridge the historical communication gap among diverse scientific and engineering disciplines by explaining how microbial processes shape subsurface water systems in an accessible, cross-disciplinary language. The book’s scope is systematically structured into three core sections: an introductory overview of microbial ecology and metabolism tailored specifically for hydrologists lacking formal biological training, an analysis of biogeochemical cycling and sampling techniques within pristine aquifers, and a final examination of contaminant biodegradation under varying reduction-oxidation (redox) conditions. By merging fundamental microbiology with practical hydrology, the publication’s key contribution is providing a comprehensive, updated framework that enables geoscientists, environmental engineers, and water planners to effectively monitor natural attenuation and implement sustainable groundwater protection and remediation strategies.