In enzymology, a guanidinopropionase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are 3-guanidinopropanoate and H<sub>2</sub>O, whereas its two products are beta-alanine and urea.
This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in linear amidines. The systematic name of this enzyme class is 3-guanidinopropanoate amidinopropionase. Other names in common use include GPase and GPH. It employs one cofactor, manganese.