In enzymology, a methylglyoxal reductase (NADH-dependent) (EC 1.1.1.78) is an enzyme that catalyzes the chemical reaction

(R)-lactaldehyde + NAD⁺ methylglyoxal + NADH + H⁺

Thus, the two substrates of this enzyme are (R)-lactaldehyde and NAD⁺, whereas its 3 products are methylglyoxal, 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 (R)-lactaldehyde:NAD⁺ oxidoreductase. Other names in common use include methylglyoxal reductase, and D-lactaldehyde dehydrogenase. This enzyme participates in pyruvate metabolism.

• Ting SM, Miller ON, Sellinger OZ (1965). "The Metabolism of lactaldehyde: VII. The oxidation of d-lactaldehyde in rat liver". Biochim. Biophys. Acta. 97: 407–15. doi:10.1016/0304-4165(65)90151-0. PMID 14323585.