In enzymology, a maleimide hydrolase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are maleimide and H<sub>2</sub>O, whereas its product is maleamic acid.
This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in cyclic amides. The systematic name of this enzyme class is cyclic-imide amidohydrolase (decyclizing). Other names in common use include imidase, cyclic imide hydrolase, and cyclic-imide amidohydrolase (decyclicizing) [misprint].