Uranium species are various forms of uranium that exist in different environments, as observed in biological systems, rocks, soils, aquatic and marine environments. In aqueous environments such as groundwater, surface water, and marine systems, uranium can occur in solution as different chemical species. Temperature is an important factor that affects the speciation of uranium in various water bodies and environments. The study of the solubility, mobility and distribution of uranium among different chemical species, such as ions, complexes, ligands and colloids, is necessary. Temperature is an essential factor in controlling or influencing the solubility of uranium, and its effects are considered in conjunction with other geochemical parameters or water chemistry parameters. The relationship between the temperature and solubility of uranium is complex and depends on various factors, such as the minerology and sources of uranium, pH concentration, redox conditions, the presence of complexing ligands, the oxidation state, speciation, salinity and the strength of ions. The solubility of uranium increases, in general, with increasing temperature. High temperatures provide greater energy for uranium ions to travel and interact with surrounding water molecules, making it very easy for uranium ions to dissolve. High temperature also affects the distribution of uranium species in solution, as uranyl ions are more soluble than other uranium species. Temperature influences the oxidation of U(IV) to U(VI) and the reduction of U(VI) to U(IV). The stability of uranium complexes with ligands such as oxides, hydroxides, carbonates, phosphates, organic complexes and colloids are influenced by temperature. Furthermore, the rates of uranium precipitation reactions, such as the formation of uranium hydroxides and uranyl phosphate, are influenced by temperature.