In enzymology, a NADPH—hemoprotein reductase is an enzyme that catalyzes the chemical reaction

NADPH + H⁺ + n oxidized hemoprotein ${\displaystyle \rightleftharpoons }$ NADP⁺ + n reduced hemoprotein

The three substrates of this enzyme are NADPH, H⁺, and oxidized hemoprotein, whereas its two products are NADP⁺ and reduced hemoprotein. It has two cofactors: flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN).

This enzyme belongs to the family of oxidoreductases, specifically those acting on NADH or NADPH with a heme protein as acceptor. The systematic name of this enzyme class is NADPH:hemoprotein oxidoreductase. Other names include cytochrome P450 reductase, ferrihemoprotein P-450 reductase, and NADPH-dependent cytochrome c reductase.

As of late 2007, 10 structures have been solved for this class of enzymes, with PDB accession codes 1AMO, 1B1C, 1J9Z, 1JA0, 1JA1, 1YQO, 1YQP, 2BF4, 2BN4, and 2BPO.