Cluster headache, nicknamed "suicide headache", is a neurological disease that involves, as its most prominent feature, an immense degree of pain in the head. Cluster headaches occur periodically: spontaneous remissions interrupt active periods of pain. The cause of the disease is currently unknown. It affects approximately 0.1% of the population, and men are more commonly affected than women.

Cluster headaches are excruciating unilateral headaches of extreme intensity.