In enzymology, (S)-carnitine 3-dehydrogenase () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are (S)-carnitine and oxidised nicotinamide adenine dinucleotide (NAD). Its products are 3-dehydrocarnitine, reduced NADH, and a proton.
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 (S)-carnitine:NAD oxidoreductase.