N-Oxalylglycine is the organic compound with the formula HO<sub>2</sub>CC(O)NHCH<sub>2</sub>CO<sub>2</sub>H. This colourless solid is used as an inhibitor of ñ-ketoglutarate-dependent enzymes. It is isosteric with ñ-Ketoglutaric acid. Such enzymes are pervasive and, for example, are required for the synthesis of 4-hydroxyproline.