<p>Rare earth elements (REEs) are essential components of modern technological advancements. With the growing industrial demand for these critical minerals, the development of efficient, selective, and sustainable extraction technologies is increasingly important. Although various processing methods are employed to extract and separate REEs from ores, efficient separation remains a challenge due to the chemical similarities among the lanthanides. This review provides a comprehensive overview of the current progress in the leaching and separation of REEs from both primary and secondary sources. Commercial solvents remain the primary reagents adopted for REEs leaching due to their exceptional efficiency, although the need for sustainability has prompted the exploration of “green” solvents. Solvent extraction (SX), which incorporates organic solvents, dominates the industrial setting. Nonetheless, technologies such as adsorption, membrane separation, and electrochemical methods demonstrate promising efficiency and sustainability. Among these, ionic liquids (ILs) are gaining attention as a promising alternative to conventional solvents for REEs extraction. ILs offer advantages including high selectivity, low volatility, and tunable chemical properties. In addition, their recyclability and relatively low environmental impact position them as a potential “green” solvent. Despite these benefits, the high synthesis costs, high viscosity, and limited solubility in water restrict their application. This review emphasizes the urgent need to promote greener technologies for the processing of these industrial “vitamins.” Advancing the current leaching and separation methods for REEs recovery is crucial to ensuring a stable and sustainable supply of REEs.</p>