In enzymology, a creatinine deaminase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are creatinine and H<sub>2</sub>O, whereas its two products are N-methylhydantoin and NH<sub>3</sub>.
This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in cyclic amidines. The systematic name of this enzyme class is creatinine iminohydrolase. Other names in common use include creatinine hydrolase, and creatinine desiminase. This enzyme participates in arginine and proline metabolism.