A near-death experience (NDE) is a profound personal event associated with death or the brink of death, characterized by common sensations such as detaching from the body, feelings of peace, encountering a light, and reviewing one's life. While these experiences share common elements, their interpretation is often shaped by an individual's cultural, philosophical, or religious background. NDEs typically occur during reversible clinical death, and explanations range from scientific hypotheses about brain function during stress to transcendental beliefs about an afterlife.

The phenomenon has been studied and described over time, with early observations in the late 19th century focusing on life reviews during falls. Later researchers like Celia Green and Elisabeth Kübler-Ross contributed to the understanding of out-of-body experiences and the broader concept of dying. The term 'near-death experience' gained prominence through the work of Raymond Moody, who identified key elements such as leaving the body, moving through a tunnel, encountering a light, and a life review, followed by a return to the body. While Moody identified fifteen elements, subsequent research has refined these into stages or common themes, emphasizing the distinction between authentic NDEs occurring during life-threatening events and other similar, but distinct, experiences.

The concept of profound experiences associated with imminent death has historical roots, with early discussions in the 1890s among psychologists and philosophers examining accounts of life reviews during falls. French psychologist Victor Egger proposed the term 'expérience de mort imminente' (experience of imminent death). Albert Heim's 1892 report detailed subjective observations from individuals who had near-death encounters, such as falls and drownings, marking the first description of the phenomenon as a clinical syndrome. In 1968, Celia Green's analysis of out-of-body experiences provided an early taxonomy. The term 'near-death experience' itself was notably used by John C. Lilly in 1972 and subsequently popularized by psychiatrist Raymond Moody in 1975, who consolidated various reported phenomena under this umbrella term.

Raymond Moody's research in 1975 identified fifteen key elements of NDEs, focusing on patients who had faced life-threatening conditions. Eleven of these elements describe the experience itself, including feelings of peace replacing pain, hearing unusual sounds, out-of-body sensations, moving through a dark tunnel, encountering a being of light, reviewing one's life, reaching a boundary, and returning to the body. Four additional elements relate to the aftermath: sharing the experience, its impact on life, altered views of death, and corroboration. Kenneth Ring later simplified these observations into a five-stage continuum: peace, body separation, entering darkness, seeing the light, and entering another realm. Recent guidelines emphasize the importance of a relation to death, transcending the material world, ineffability, and beneficial life changes as core characteristics of authentic NDEs.

The interpretation of a near-death experience is significantly influenced by an individual's cultural, philosophical, and religious beliefs; for instance, the 'light' may be perceived as angels or divine messengers depending on the person's background. Modern research highlights the need to distinguish between authentic NDEs, which occur during critical physiological states like cardiac arrest and are characterized by coherence and profound impact, and 'mislabeled' NDEs. The latter can arise from various medical or non-medical conditions, including anesthesia, drug use (like ketamine or DMT), dreams, or seizures, and often lack the consistent narrative structure, transcendent qualities, and transformative effects of genuine NDEs. Negative or 'hellish' experiences are also generally considered distinct from classical NDEs, often being better explained as ICU delirium or delusions.