A herniated disc (prolapse, disc herniation) is the displacement of parts of the nucleus pulposus through the damaged fibrous ring of the disc into the spinal canal or the intervertebral foramen.

The lower lumbar segments and the cervical spine are most commonly affected. Clinically, there may be local back pain, pain radiating into the leg or arm, sensory disturbances and loss of strength. It must be distinguished from a disc bulge (protrusion), in which the fibrous ring remains intact.