In enzymology, a phosphonoacetaldehyde hydrolase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are phosphonoacetaldehyde and H<sub>2</sub>O, whereas its two products are acetaldehyde 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 2-oxoethylphosphonate phosphonohydrolase. Other names in common use include phosphonatase, and 2-phosphonoacetylaldehyde phosphonohydrolase. This enzyme participates in aminophosphonate metabolism.
As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and .