A carbonate ester is a functional group in organic chemistry consisting of a carbonyl group flanked by two alkoxy groups. The general structure of these carbonates is (R₁O)(R₂O)C=O and they are related to esters (R₁O)(R)C=O and ethers (R₁O)(R₂O)C and also to the inorganic carbonates.

Carbonate esters are used as protecting group for diols. A classic reagent is phosgene but more user friendly reagents exist such as carbonyl diimidazole.

Polycarbonates are an important class of polymers.

functional groups