Steady‐State Atomic Configuration Control Enables Universal Synthesis of High‐Entropy Alloy Nanoparticles via Radish

High‐entropy alloy nanoparticles (HEA‐NPs) promise superior catalysis, yet scalable synthesis of compositionally uniform nanoparticles remains a major challenge due to inevitable elemental segregation in conventional high‐temperature melting or carbothermal shock methods. In this study, a biomass‐mediated steady‐state synthesis strategy was developed by integrating freeze‐drying with in situ carbonization‐reduction, using radish as both a structural scaffold and a green reducing/carbon source. This near‐equilibrium approach effectively eliminates high‐temperature processing, suppresses pre‐reduction metal ion segregation, and yields strictly atomic‐level uniform HEA‐NPs across binary to denary compositions. The benchmark PtPdFeCoNi HEA‐NPs achieved 100 mA cm −2 at only 97 mV overpotential in acidic hydrogen evolution, with 76.5% activity retention after 24 h, markedly outperforming commercial Pt/C. The steady‐state method is universally applicable across 2–10 metal components while maintaining single‐phase solid‐solution structures. This work overcomes the long‐standing bottleneck in scalable synthesis of homogeneous HEA‐NPs and provides a versatile, equipment‐simple platform for producing next‐generation multicomponent nanocatalysts.