In enzymology, a cytochrome-c3 hydrogenase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are H<sub>2</sub> and ferricytochrome c3, whereas its two products are H<sup>+</sup> and ferrocytochrome c3.
This enzyme belongs to the family of oxidoreductases, specifically those acting on hydrogen as donor with a cytochrome as acceptor. The systematic name of this enzyme class is hydrogen:ferricytochrome-c3 oxidoreductase. Other names in common use include H2:ferricytochrome c3 oxidoreductase, cytochrome c3 reductase, cytochrome hydrogenase, and hydrogenase [ambiguous]. It has 3 cofactors: iron, Nickel, and Iron-sulfur.
As of late 2007, 19 structures have been solved for this class of enzymes, with PDB accession codes , , , , , , , , , , , , , , , , , , and .