In enzymology, a trimetaphosphatase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are trimetaphosphate and H<sub>2</sub>O, whereas its product is triphosphate.
This enzyme belongs to the family of hydrolases, specifically those acting on acid anhydrides in phosphorus-containing anhydrides. The systematic name of this enzyme class is trimetaphosphate hydrolase. This enzyme is also called inorganic trimetaphosphatase. This enzyme participates in pyrimidine metabolism.