• BCC high-entropy alloys (HEAs) enable multiscale regulation of thermodynamics and kinetics, offering a promising pathway to overcome the capacity–stability trade-offs of conventional hydrogen storage alloys.
• Composition screening via empirical descriptors, CALPHAD thermodynamic modeling, and machine learning accelerates the rational design of high-performance BCC HEAs.
• Processing routes such as melting, mechanical alloying, and emerging methods control chemical homogeneity and defect structures, critically influencing hydrogen storage behavior.
• Hydrogen storage performance in BCC HEAs is determined by activation, thermodynamics, kinetics, and cyclic stability, with mechanistic origins linked to lattice distortion and local chemical environments.