Electrocatalytic water splitting is a promising approach for clean hydrogen production, but the process is hindered by the sluggish kinetics of the anodic oxygen evolution reaction (OER) owing to the spin-dependent electron transfer process. Efforts to control spin through chirality and magnetization have shown potential in enhancing OER performance. Here we harnessed the potential of topological chiral semimetals (RhSi, RhSn and RhBiS) and their spin-polarized Fermi surfaces to promote the spin-dependent electron transfer in the OER, addressing the traditional volcano-plot limitations. We show that OER activities follow the trend RhSi < RhSn < RhBiS, corresponding to the increasing extent of spin–orbit coupling (SOC). The chiral single crystals outperform achiral counterparts (RhTe₂, RhTe and RuO₂) in alkaline electrolyte, with RhBiS exhibiting a specific activity two orders of magnitude higher than RuO₂. Our work reveals the pivotal roles of chirality and SOC in spin-dependent catalysis, facilitating the design of ultra-efficient chiral catalysts.