Alkali catalysis denotes catalysis in which a compound or complex of lithium, sodium, potassium, rubidium, or cesium participates in the turnover-determining activation of an organic substrate. The catalytic species commonly behaves as a Brønsted base, nucleophile, Lewis acid, or ion-pairing counterion rather than undergoing the multivalent redox cycles typical of transition metals. Alkali-metal identity is mechanistically significant because ionic radius, aggregation, solvation, and contact-ion pairing alter substrate binding and the reactivity of anionic intermediates. Well-defined heavier alkali-metal complexes can mediate both stoichiometric and catalytic organic transformations ^[1], while alkali-metal tert-butoxides can function directly as catalysts or as activators in carbon–carbon and carbon–heteroatom bond formation ^[2]. The term requires regeneration of the alkali-containing active species; use of an alkali reagent in a single stoichiometric deprotonation is not, by itself, alkali catalysis. Heterogeneous alkali catalysis is the solid-phase subset of this broader category.