Sulfite reductases (EC 1.8.99.1) are enzymes that participate in sulfur metabolism.

[2][3] Electrons for the reaction are provided by a dissociable molecule of either NADPH, bound flavins, or ferredoxins.

[4] Sulfite reductases, which belong to the oxidoreductase family, are found in the archaea, bacteria, fungi, and plants.

This enzyme participates in selenoamino acid metabolism and sulfur assimilation.

[8] The systematic name of this enzyme class is hydrogen-sulfide:acceptor oxidoreductase.