The oxoglutarate dehydrogenase complex (OGDC) or α-ketoglutarate dehydrogenase complex is a mitochondrial multienzyme complex, most commonly known for its role in the citric acid cycle. It belongs to the 2-oxoacid dehydrogenase complex family.

Much like pyruvate dehydrogenase complex (PDC), this enzyme forms a complex composed of three components:

Four members of these multienzyme complexes have been characterized: one specific for pyruvate, a second specific for 2-oxoglutarate, a third specific for 2-oxoadipate, and a fourth specific for branched-chain α-keto acids. The oxoglutarate dehydrogenase complex has the same subunit structure and thus uses the same cofactors (TPP, CoA, lipoate, FAD and NAD) as:

Among these, OGDC and OADHC are particularly closely related, as they not only share the same E2 and E3 components, but also catalyze chemically similar reactions within adjacent steps of lysine and tryptophan catabolism. Notably, all four complexes rely on a common E3 subunit that is also employed by the glycine cleavage system (GCS) in the form of its L-protein, despite the GCS not belonging to this enzyme family.

This enzyme participates in three different pathways:

The following values are from Azotobacter vinelandii ⁽¹⁾:

The reaction catalyzed by this enzyme in the citric acid cycle is:

This reaction proceeds in three steps: