Rare Earth Elements (REE) are a group of 16 chemically similar elements that are widespread in rocks, soils, and water bodies. They share similar ionic radii with calcium and are thus present in biota. As trivalent cations, they resemble aluminum and have higher reactivity than calcium, potentially causing environmental harm. The increasing use of REE in technology and fertilizers has raised concerns about soil and water pollution, leading to extensive research on their toxicity, fate in soil-plant systems, and impacts on food security. This review provides an overview of current knowledge on REE occurrence, environmental processes governing their mobility, and transfer into biota. It covers their distribution in the lithosphere, pedosphere, hydrosphere, and biosphere, including impacts on food security and public health. Analytical methods for REE determination include nuclear techniques like neutron activation analysis and ICP-MS. These methods face challenges due to low concentrations, stable minerals, and matrix interferences. Sequential leaching methods are used to assess REE mobility and plant availability, revealing that mobile fractions correlate with plant uptake. REE in sediments are influenced by lithology, weathering, and erosion, with high concentrations in certain areas. Marine sediments show varying REE patterns depending on environmental conditions. Coal and coal ash contain significant REE concentrations, with combustion leading to enrichment. In soils, REE concentrations depend on parent material, climate, and biological activity. Mobility is influenced by ionic radii, speciation, pH, and mineral composition. REE sorption on clay, phosphates, and organic matter reduces their mobility, while ligands can increase solubility. REE in soils are often sequestered in organic matter, with variations in concentration depending on soil type and conditions. Overall, REE play a significant role in environmental processes, and their management is crucial for mitigating potential ecological impacts.Rare Earth Elements (REE) are a group of 16 chemically similar elements that are widespread in rocks, soils, and water bodies. They share similar ionic radii with calcium and are thus present in biota. As trivalent cations, they resemble aluminum and have higher reactivity than calcium, potentially causing environmental harm. The increasing use of REE in technology and fertilizers has raised concerns about soil and water pollution, leading to extensive research on their toxicity, fate in soil-plant systems, and impacts on food security. This review provides an overview of current knowledge on REE occurrence, environmental processes governing their mobility, and transfer into biota. It covers their distribution in the lithosphere, pedosphere, hydrosphere, and biosphere, including impacts on food security and public health. Analytical methods for REE determination include nuclear techniques like neutron activation analysis and ICP-MS. These methods face challenges due to low concentrations, stable minerals, and matrix interferences. Sequential leaching methods are used to assess REE mobility and plant availability, revealing that mobile fractions correlate with plant uptake. REE in sediments are influenced by lithology, weathering, and erosion, with high concentrations in certain areas. Marine sediments show varying REE patterns depending on environmental conditions. Coal and coal ash contain significant REE concentrations, with combustion leading to enrichment. In soils, REE concentrations depend on parent material, climate, and biological activity. Mobility is influenced by ionic radii, speciation, pH, and mineral composition. REE sorption on clay, phosphates, and organic matter reduces their mobility, while ligands can increase solubility. REE in soils are often sequestered in organic matter, with variations in concentration depending on soil type and conditions. Overall, REE play a significant role in environmental processes, and their management is crucial for mitigating potential ecological impacts.