In enzymology, a 3-hydroxybutyrate dehydrogenase (EC 1.1.1.30) is an enzyme that catalyzes the chemical reaction: (R)-3-hydroxybutanoate + NAD+ ? acetoacetate + NADH + H+. Thus, the two substrates of this enzyme are (R)-3-hydroxybutanoate and NAD+, whereas its three products are acetoacetate, NADH, and H+. This enzyme belongs to the family of oxidoreductases, to be specific, those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor.