Arsenic-contaminated groundwater, a global health threat, poses significant health risks for millions worldwide. The complex biogeochemical processes that control arsenic mobility and toxicity often render traditional remediation methods inadequate. However, the field of geomicrobiology, a study of microbial–mineral interactions, offers a beacon of hope in the form of potential solutions for addressing arsenic contamination. This study delves into the processes that occur during the cycling of arsenic in groundwaters, investigating how microorganisms influence the mobilization and immobilization of arsenic and its speciation. By understanding these microbial agents, we can devise more effective methods of monitoring and remediating arsenic-contaminated groundwater. The chapter presents a comprehensive survey of current research, identifies critical microbes, and proposes innovative strategies for harnessing geomicrobes to eliminate arsenic from water systems. This extensive framework aims to enhance our understanding of geomicrobiological mechanisms and leverage them to develop more efficient and sustainable techniques for managing arsenic-contaminated water supplies. It unveils new paradigms and practical solutions to address one of the most pressing global environmental health issues related to mineral-microbial relationships.