Clinical death is the medical term for cessation of blood circulation and breathing, the two necessary criteria to sustain life. It occurs when the heart stops beating in a regular rhythm, a condition called cardiac arrest. The term is also sometimes used in resuscitation research.

Stopped blood circulation has historically proven irreversible in most cases. Prior to the invention of cardiopulmonary resuscitation (CPR), defibrillation, epinephrine injection, and other treatments in the 20th century, the absence of blood circulation (and vital functions related to blood circulation) was historically considered to be the official definition of death. With the advent of these strategies, cardiac arrest came to be called "clinical death" rather than simply "death" to reflect the possibility of post-arrest resuscitation; for medical purposes, it is considered to be the final physical state before permanent death.^{[citation needed]}

At the onset of clinical death, consciousness is lost within several seconds. Measurable brain activity stops within 20 to 40 seconds.Irregular gasping may occur during this early time period, and is sometimes mistaken by rescuers as a sign that CPR is not necessary. During clinical death, all tissues and organs in the body steadily accumulate a type of injury called ischemic injury.