In enzymology, lactaldehyde dehydrogenase () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are (S)-lactaldehyde, oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>), and water. Its products are (S)-lactic acid, reduced NADH, and a proton.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the aldehyde or oxo group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (S)-lactaldehyde:NAD+ oxidoreductase. Other names in common use include L-lactaldehyde:NAD+ oxidoreductase, and nicotinamide adenine dinucleotide (NAD+)-linked dehydrogenase. This enzyme participates in pyruvate metabolism.
As of late 2007, 4 structures have been solved for this class of enzymes, with PDB accession codes , , , and .