In enzymology, a fructuronate reductase (EC1.1.1.57) is an enzyme that catalyzes the chemical reaction

Thus, the two substrates of this enzyme are D-mannonate and NAD, whereas its 3 products are D-fructuronate, NADH, and H.

This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD or NADP as acceptor. The systematic name of this enzyme class is D-mannonate:NAD 5-oxidoreductase. Other names in common use include mannonate oxidoreductase, mannonic dehydrogenase, D-mannonate dehydrogenase, and D-mannonate:NAD oxidoreductase. This enzyme participates in pentose and glucuronate interconversions.