Polychlorinated biphenyls (PCBs) persist globally as legacy pollutants with a complex structural diversity that complicates the understanding of their microbial conversion processes and remediation. In this study, high-throughput enzymatic assays, quantum chemical calculations, and machine learning were integrated to elucidate the reductive dechlorination pathways and reactivity of all 209 PCB congeners. By coupling Hirshfeld charge analysis with empirically derived steric effects, 98.3% accurac