Abstract: The efficient separation and recovery of neptunium(Np), one of the most chemically complex actinides in the nuclear fuel cycle, represent a critical challenge in spent nuclear fuel reprocessing and advanced fuel-cycle management. Effective control of Np behavior is essential not only for improving the sustainability and economics of nuclear energy systems, but also for minimizing the long-term radiotoxicity of radioactive waste and supporting the implementation of a closed nuclear fuel cycle. Among the known neptunium isotopes, ²³⁷Np is of particular importance because of its long half-life(2.1×10⁶ years), high radiotoxicity, and potential application as a precursor for the production of ²³⁸Pu, which is widely used as a heat source in radioisotope thermoelectric generators. However, the extraction and separation of Np remain exceptionally difficult owing to its complicated electronic structure and the coexistence of multiple oxidation states, including Np(Ⅲ), Np(Ⅳ), Np(Ⅴ), Np(Ⅵ), and Np(Ⅶ), whose stability and chemical behavior strongly depend on solution composition, acidity, redox conditions, and coordinating ligands. This review provides a comprehensive overview of recent advances in Np extraction and separation technologies for spent nuclear fuel reprocessing. The fundamental chemistry of neptunium, particularly its redox properties and valence-state transformations, is first summarized to establish the theoretical basis for separation processes. Subsequently, the major extraction and recovery approaches, including precipitation, solid-phase adsorption, membrane-based separation, and solvent extraction, are systematically reviewed and compared with respect to their separation mechanisms, process efficiencies, advantages, and limitations. Particular attention is given to solvent-extraction technologies because of their dominant role in industrial reprocessing. Recent developments involving tributyl phosphate, monoamides, diglycolamides, triazine-based ligands, and other functional extractants are discussed in detail. In addition, strategies based on valence-state control, including chemical, electrochemical, and photochemical methods, are critically evaluated because precise manipulation of Np oxidation states is often the key factor determining its distribution and recovery behavior. The review further summarizes representative advanced reprocessing flowsheets developed worldwide, including UREX+(NPEX), PARC, APOR, and other Np-oriented separation schemes. Their process configurations, separation principles, Np routing characteristics, and engineering performance are analyzed and compared. Particular emphasis is placed on the use of salt-free organic reductants, selective complexants, and integrated process-control strategies that enable more efficient and environmentally benign Np management. The major technical barriers to industrial implementation are also discussed, including the complexity of Np redox chemistry, limitations in extractant selectivity and radiation stability, process integration challenges, and the generation of secondary waste streams. Finally, future research directions are proposed, including deeper investigation of fundamental Np chemistry in diverse process environments, development of highly selective and radiation-resistant functional materials, advancement of intelligent process monitoring and control technologies, and integration of innovative separation strategies into next-generation reprocessing flowsheets. This review aims to provide a comprehensive theoretical and technical reference for improving Np recovery efficiency, enhancing nuclear fuel cycle safety, and promoting the realization of sustainable closed nuclear fuel cycle systems.