In enzymology, 2-hydroxymethylglutarate dehydrogenase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are (S)-2-hydroxymethylglutaric acid and oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>). Its products are 2-formylglutaric acid, reduced NADH, and a proton.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD<sup>+</sup> or NADP<sup>+</sup> as acceptor. The systematic name of this enzyme class is (S)-2-hydroxymethylglutarate:NAD<sup>+</sup> oxidoreductase. This enzyme is also called HgD.