In enzymology, 7alpha-hydroxysteroid dehydrogenase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are the bile acid, cholic acid, and oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>). Its products are 7-ketodeoxycholic acid, 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 7alpha-hydroxysteroid:NAD<sup>+</sup> 7-oxidoreductase. Other names in common use include 7alpha-hydroxy steroid dehydrogenase, and 7alpha-HSDH.
As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes , , and .