Rhodium (Rh)-based catalysts have shown superior potential over platinum for the alkaline electrocatalytic hydrogen evolution reaction (HER). However, achieving high catalytic activity while minimizing Rh usage remains a significant challenge. Herein, we anchored 1.48 wt.% Rh clusters onto nickel-iron layered double hydroxides with cationic defects. The Rh clusters exhibit multiple highly reactive crystallographic facets, providing numerous active sites for catalytic reactions. The cationic vacancies facilitate efficient charge transfer between the Rh clusters and the support through Rh–O bonds, lowering the d-band center of Rh and optimizing hydrogen adsorption strength. Consequently, the synthesized catalyst demonstrates exceptional performance, achieving an ultra-low overpotential of 4 mV at 10 mA·cm⁻², surpassing all previously reported Rh-based catalysts. This work presents a promising strategy for designing cost-effective and highly efficient alkaline HER catalysts.