In enzymology, a phosphonoacetate hydrolase (EC 3.11.1.2) is an enzyme that catalyzes the chemical reaction

phosphonoacetate + H₂O ${\displaystyle \rightleftharpoons }$ acetate + phosphate

Thus, the two substrates of this enzyme are phosphonoacetate and H₂O, whereas its two products are acetate and phosphate.

This enzyme belongs to the family of hydrolases, specifically those acting on carbon-phosphorus bonds. The systematic name of this enzyme class is phosphonoacetate phosphonohydrolase. This enzyme participates in aminophosphonate metabolism. It employs one cofactor, zinc.

The structure of this enzyme, with the PDB accession code 1EI6, shows it adopts the alkaline phosphatase fold.