In enzymology, an urethanase (EC 3.5.1.75) is an enzyme that catalyzes the chemical reaction

urethane + H₂O ${\displaystyle \rightleftharpoons }$ ethanol + CO₂ + NH₃

Thus, the two substrates of this enzyme are urethane and H₂O, whereas its 3 products are ethanol, CO₂, and NH₃.

This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in linear amides. The systematic name of this enzyme class is urethane amidohydrolase (decarboxylating). This enzyme is also called urethane hydrolase.