In the Earth, redox processes are ubiquitous from the core/mantle boundary to the hydrosphere/atmosphere, and help provide the energy to power non-photosynthetic life. The goal of this study is to develop tools to use stable isotopes as quantitative markers for redox processes. I will present our experimental studies on a variety of metal systems (e.g. Fe, Zn, Li, etc.) that demonstrate a large kinetic isotope effect associated with redox processes. In addition, I will also present a theoretical framework that predicts a kinetic isotope fractionation arising from simple electrochemical reactions. ?