In enzymology, a L-threonine 3-dehydrogenase (EC 1.1.1.103) is an enzyme that catalyzes the chemical reaction Thus, the two substrates of this enzyme are L-threonine and NAD+, whereas its 3 products are L-2-amino-3-oxobutanoate, 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 L-threonine:NAD+ oxidoreductase.

This enzyme participates in glycine, serine and threonine metabolism.

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes 2D8A, 2DFV, and 2DQ4.