In enzymology, a hydroxymalonate dehydrogenase (EC 1.1.1.167) is an enzyme that catalyzes the chemical reaction

hydroxymalonate + NAD⁺ ${\displaystyle \rightleftharpoons }$ oxomalonate + NADH + H⁺

Thus, the two substrates of this enzyme are hydroxymalonate and NAD⁺, whereas its 3 products are oxomalonate, NADH, and H⁺.

This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD⁺ or NADP⁺ as acceptor. The systematic name of this enzyme class is hydroxymalonate:NAD⁺ oxidoreductase.