An acetate (IUPAC name: ethanoate) is either a salt or an ester of acetic acid. Its formula is written both as CH3CO2− and C2H3O2−.

Chemists abbreviate acetate as OAc− and AcO−. Thus HOAc is the abbreviation for acetic acid, NaOAc for sodium acetate, and EtOAc for ethyl acetate Acetate is a common anion in biology.