In enzymology, a hydroxymalonate dehydrogenase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are tartronic acid and oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>). Its products are mesoxalic 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 hydroxymalonate:NAD<sup>+</sup> oxidoreductase.