This book provides a comprehensive summary of research to date in the field of stable iron isotope geochemistry. Since research began in this field 20 years ago, the field has grown to become one of the major research fields in “non-traditional” stable isotope geochemistry. This book reviews all aspects of the field, from low-temperature to high-temperature processes, biological processes, and cosmochemical processes. It provides a detailed history and state-of-the art summary about analytical methods to determine Fe-isotope ratios and discusses analytical and sample prospects.