The Red nucleus is a brainstem structure associated with the upper motor system and involved with movement.

It is appropriately named "red" because its superficial appearance is red because of the rich capillary beds that supply it.

The red nucleus sends axons down that transverse to the contralateral side of the body in the brainstem, and these axons project to lateral parts of the spinal cord and are concerned with precise movements and a single axon bundle spans only several spinal cord segments, and are restricted to the cervical spinal cord segments. The axonal projects of the red nucleus are termed the rubrospinal tract.

The red nucleus of humans is particularily pronounced compared to other animals.