The Darzens reaction (also known as the Darzens condensation or glycidic ester condensation) is the chemical reaction of a ketone or aldehyde with an α-haloester in the presence of base to form an α,β-epoxy ester, also called a "glycidic ester". This reaction was discovered by the organic chemist Auguste George Darzens in 1904.<ref name=darzens1905">Darzens, G. (1905). "Methode generale de synthese des d'esters glycidiques αβ substitues et de cetones". Compt. Rend. (in French) 141: 766. </ref><ref name=darzens1906">Darzens, G. (1906). "Condensation glycidique des aldehydes avec l'ether alpha-chloropropionique". Compt. Rend. (in French) 142: 214. </ref>