Redox potential (oxidation–reduction potential, ORP), a measure of a system’s reducing or oxidizing capacity, plays a vital role in determining the fate of uranium in different environments and its impact on human health and ecosystem stability. The ORP influences uranium’s oxidation state, solubility and mobility, bioavailability, and contamination potential in natural ecosystems. Uranium, a naturally occurring radionuclide heavy metal found in soil, rock, and water, exists primarily in both mobile and immobile phases depending on its two oxidation states: highly soluble and mobile uranium(VI) and less soluble and less mobile uranium(IV). Under oxidizing conditions (oxic, high redox potential), uranium is present mainly in the form of uranium(VI), increasing the risk of environmental and health issues. Conversely, under reducing conditions (suboxic to anoxic, low redox potential), uranium tends to favor the formation of uranium(IV), leading to lower solubility and mobility. Other factors, such as pH, organic matter, and microbial activity, can also influence uranium behavior in the environment, hence providing different implications concerning the contamination of water resources. A broadened understanding of uranium redox chemistry in water resources and the impact of redox potential on uranium mobility are crucial for the development of mitigation frameworks and effective remediation strategies. This chapter explores the complex chemistry of uranium redox and its solubility in various water bodies, as well as the speciation of uranium at the soil–water interface, offering a broad understanding of ORP dynamics and their relationship with uranium chemistry to address uranium contamination and safeguard environmental and human health.