In enzymology, a galactitol 2-dehydrogenase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are galactitol and oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>). Its products are D-tagatose, 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 galactitol:NAD<sup>+</sup> 2-oxidoreductase. This enzyme is also called dulcitol dehydrogenase. This enzyme participates in galactose metabolism.