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Heterogeneous alkali catalysis uses a solid catalyst containing alkali or strongly basic metal–oxygen sites while the reactants occupy a separate liquid or gas phase. Representative materials include alkali-metal compounds dispersed on oxides, alkali-exchanged zeolites, mixed oxides, and related solids whose surface O₂−, OH−, or supported alkoxide sites abstract protons or donate electron density. Catalytic behavior depends on the number, strength, accessibility, and local coordination of surface basic sites; alkali cations can also modify adsorption and stabilize surface anions. Structure-focused reviews classify solid basic catalysts by the identity, strength, and geometry of their basic sites ^[1]. Broader surveys relate those sites to heterogeneous condensation, isomerization, Michael addition, and transesterification chemistry ^[2]. The catalyst must remain a distinct phase and be regenerated during turnover. This distinguishes the concept from homogeneous alkali catalysis by dissolved hydroxides or alkoxides and from heterogeneous transition-metal redox catalysis, in which electron-transfer steps at multivalent metal centers define the cycle.