The interpeduncular nucleus (IPN) is an unpaired, ovoid group of neurons at the base of the midbrain tegmentum. In the midbrain it lies below the interpeduncular fossa. As the name suggests, the interpeduncular nucleus lies in between the cerebral peduncles.

The Interpeduncular nucleus is primarily GABAergic and contains at least two neuron clusters of different morphologies. The region is divided into 7 paired and unpaired subnuclei

The presence of non-homologous subdivisions of the Interpeduncular nucleus was first noticed by Cajal over a hundred years ago. The currently recognized standard subdivision notation was mostly established by Hammill and Lenn in 1984 by combining the work and notations of four groups. Although most of their proposed convention stuck, at some point the proposed "rostral lateral" sub-nucleus was renamed "dorsomedial" and became immortalized in brain atlases.

Unpaired sub-nucleus. Former names include: "caudal dorsal", "dorsal", and "pars dorsalis magnocellularis".

Unpaired sub-nucleus. Former names include: "rostral ventral", "caudal central", "posterior inter", and "pars medianus".

Paired sub-nucleus.

Paired sub-nucleus. Former names include: "rostral lateral" and "interstitial".

Paired sub-nucleus. Former names include: "caudal intermediate", "posterior inner" and "pars medianus".