In enzymology, an oxalate decarboxylase () is an oxalate degrading enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are oxalate and H<sup>+</sup>, whereas its two products are formate and CO<sub>2</sub>.
This enzyme belongs to the family of lyases, specifically the carboxy-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is oxalate carboxy-lyase (formate-forming). This enzyme is also called oxalate carboxy-lyase. This enzyme participates in glyoxylate and dicarboxylate metabolism.
As of late 2007, 5 structures have been solved for this class of enzymes, with PDB accession codes , , , , and .