In enzymology, a 4-hydroxybutyrate dehydrogenase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are 4-hydroxybutanoic acid, and oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>). Its products are succinic semialdehyde, 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 4-hydroxybutanoate:NAD<sup>+</sup> oxidoreductase. This enzyme is also called gamma-hydroxybutyrate dehydrogenase. This enzyme participates in butanoate metabolism and the degradation of the neurotransmitter 4-hydroxybutanoic acid.