This study introduces a high-entropy hexacyanoferrate (HE-HCF) material for capacitive deionization (CDI) applications, which significantly improves the desalination capacity and cycling stability of Prussian blue analogs (PBAs). By incorporating five or more metals into the PBA structure, HE-HCF achieves a high configurational entropy of over 1.5R, enhancing structural stability and ion diffusion. The HE-HCF demonstrates an exceptional desalination capacity of 77.24 mg g⁻¹ at 1.2 V and retains over 97% of its capacity after 350 cycles. Structural and theoretical analyses reveal that the high entropy suppresses phase transitions, optimizes Na⁺ diffusion pathways, and accelerates reaction kinetics. The HE-HCF also exhibits a high specific capacitance of 280.4 F g⁻¹ at 0.5 mV s⁻¹ and a low charge transfer resistance, contributing to its excellent electrochemical performance. Compared to other materials, HE-HCF shows superior desalination efficiency and cycling stability, making it a promising candidate for long-term CDI applications. The entropy engineering strategy provides a new approach to design high-performance, cost-effective, and durable electrodes for CDI.This study introduces a high-entropy hexacyanoferrate (HE-HCF) material for capacitive deionization (CDI) applications, which significantly improves the desalination capacity and cycling stability of Prussian blue analogs (PBAs). By incorporating five or more metals into the PBA structure, HE-HCF achieves a high configurational entropy of over 1.5R, enhancing structural stability and ion diffusion. The HE-HCF demonstrates an exceptional desalination capacity of 77.24 mg g⁻¹ at 1.2 V and retains over 97% of its capacity after 350 cycles. Structural and theoretical analyses reveal that the high entropy suppresses phase transitions, optimizes Na⁺ diffusion pathways, and accelerates reaction kinetics. The HE-HCF also exhibits a high specific capacitance of 280.4 F g⁻¹ at 0.5 mV s⁻¹ and a low charge transfer resistance, contributing to its excellent electrochemical performance. Compared to other materials, HE-HCF shows superior desalination efficiency and cycling stability, making it a promising candidate for long-term CDI applications. The entropy engineering strategy provides a new approach to design high-performance, cost-effective, and durable electrodes for CDI.