Decapitation (from Latin, caput, capitis, meaning head) is the separation of the head from the body. Beheading typically refers to the act of intentional decapitation, e.g., as a means of murder or execution; it may be accomplished, for example, with an axe, sword, knife, wire, or by other more sophisticated means such as a guillotine. Ritualistic decapitation after execution by some other means, sometimes followed by public display of the severed head, has also been common throughout history. An executioner carrying out decapitations is called a headsman. Accidental decapitation can be the result of an explosion, car or industrial accident, improperly administered execution by hanging or other violent injury. Suicide by decapitation is rare, but not unknown.

Decapitation is quickly fatal to humans and most animals as brain death occurs within minutes without circulating oxygenated blood. However, some animals and insects (such as cockroaches) can survive decapitation, and die not because of the loss of the head directly, but rather because of starvation. Although head transplantation by the reattachment of blood vessels has been successful with animals, a fully functional reattachment of a severed human head (including repair of the spinal cord, muscles, and other critically important tissues) has not been achieved.