Enantioselective catalysis is catalysis in which a chiral catalyst causes two enantiomer-forming pathways to proceed at different rates, thereby producing an enantiomerically enriched product from an achiral, prochiral, or racemic substrate. The stereochemical discrimination occurs through diastereomeric catalyst–substrate transition states or intermediates, and the catalyst is regenerated after product formation. Chiral metal complexes, chiral organic molecules, and enzymes are the principal catalyst classes used for this purpose ^[1]. Enantioselectivity is quantified by the product enantiomeric ratio or enantiomeric excess and reflects the free-energy difference between competing stereodetermining pathways. The term is narrower than asymmetric synthesis, which also includes stoichiometric chiral reagents, auxiliaries, and resolutions. It is also distinct from ordinary diastereoselective catalysis of an already chiral substrate unless the catalyst itself controls selection between enantiomeric outcomes. Structure–selectivity relationships describe how catalyst features alter this kinetic discrimination ^[2].