Oxalate (IUPAC: ethanedioate) is an anion with the formula C₂O₄²⁻. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na₂C₂O₄), and several esters such as dimethyl oxalate (C₂O₄(CH₃)₂). It is a conjugate base of oxalic acid. At neutral pH in aqueous solution, oxalic acid converts completely to oxalate.