Caesium carbonate or cesium carbonate is a chemical compound with the chemical formula Cs₂CO₃. It is white crystalline solid. Caesium carbonate has a high solubility in polar solvents such as water, ethanol and DMF. Its solubility is higher in organic solvents compared to other carbonates like potassium carbonate and sodium carbonate, although it remains quite insoluble in other organic solvents such as toluene, p-xylene, and chlorobenzene. This compound is used in organic synthesis as a base. It also appears to have applications in energy conversion.

Caesium carbonate can be prepared by thermal decomposition of caesium oxalate. Upon heating, caesium oxalate is converted to caesium carbonate with emission of carbon monoxide.

It can also be synthesized by reacting caesium hydroxide with carbon dioxide.

Caesium carbonate facilitates the N-alkylation of compounds such as sulfonamides, amines, β-lactams, indoles, heterocyclic compounds, N-substituted aromatic imides, phthalimides, and other similar compounds.

Caesium carbonate and copper(II) chloride are used in the aerobic oxidation of primary alcohols.

Caesium carbonate can also be used in Suzuki, Heck, and Sonogashira coupling reactions.^{[citation needed]}

Caesium carbonate produces carbonylation of alcohols and carbamination^{[clarification needed]} of amines more efficiently than some of the mechanisms that have been introduced in the past.

Caesium carbonate can be used for sensitive synthesis when a balanced strong base is needed.^{[citation needed]}