In enzymology, orotate reductase (NADH) () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are (S)-dihydroorotic acid and oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>). Its products are orotic acid, reduced NADH, and a proton.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (S)-dihydroorotate:NAD+ oxidoreductase. This enzyme is also called orotate reductase (NADH). This enzyme participates in pyrimidine metabolism. It has 2 cofactors: flavin adenine dinucleotide, and flavin mononucleotide.