An out-of-body experience (OBE or sometimes OOBE), is an experience that typically involves a sensation of floating outside of one's body and, in some cases, perceiving one's physical body from a place outside one's body (autoscopy). The term out-of-the-body experience was introduced in 1943 by G.N.M Tyrrell in his book Apparitions, and adopted by, for example, Celia Green and Robert Monroe as a bias-free alternative to belief-centric labels such as "astral projection" or "spirit walking".

Though the term usefully distances researchers from scientifically problematic concepts such as the soul, scientists still know little about the phenomenon. One in ten people has an out-of-body experience at some time in their lives. OBEs are often part of the near-death experience, and reportedly may also lead to astral projection. Those who have experienced OBEs sometimes claim to have observed details which were unknown to them beforehand.

In some cases the phenomenon appears to occur spontaneously; in others it is associated with a physical or mental trauma, use of psychedelic drugs, dissociative drugs, or a dream-like state. Many techniques aiming to induce the experience deliberately have been developed[7], for example visualization while in a relaxed, meditative state. Recent (2007) studies have shown that experiences somewhat similar to OBEs can be induced by direct brain stimulation. Some of those who experience OBEs claimed to have willed themselves out of their bodies, while others report having found themselves being pulled from their bodies (usually preceded by a feeling of paralysis). In other accounts, the feeling of being outside the body was suddenly realized after the fact, and the experiencers saw their own bodies almost by accident. OBEs often occur during the borderline stage between REM sleep and arousal when sleep paralysis may persist and dream imagery may mingle with sensory input.

Some neurologists have suspected that the event is triggered by a mismatch between visual and tactile signals. They used a virtual reality setup to recreate an OBE. The subject looked through goggles and saw his own body as it would appear to an outside observer standing behind him. The experimenter then touched the subject at the same time as a rod appeared to touch the virtual image. The experiment created an illusion of being behind and outside one's body. However, critics point out that it is uncertain how this relates to the OBE phenomenon.

OBEs are sometimes reported to be preceded by and initiated from a lucid dream state, though other types of immediate and spontaneous experience are also reported. In many cases, people who claimed to have had an OBE reported being asleep, on the verge of sleep, or already asleep shortly before the experience. A large percentage of these cases referred to situations where the sleep was not particularly deep (due to illness, noises in other rooms, emotional stress, exhaustion from overworking, frequent re-awakening, etc.). In most of these cases, the subjects then felt themselves awake; about half of them noted a feeling of sleep paralysis.

Astral projection is a paranormal interpretation of out-of-body experience that assumes the existence of one or more non-physical planes of existence and an associated body beyond the physical. Commonly such planes are called astral, etheric, or spiritual. Astral projection is often experienced as the spirit or astral body leaving the physical body to travel in the spirit world or astral plane.

Evidence for objective reality of projection on to the etheric plane (a near-copy of the physical plane) is sometimes suggested when people, such as patients during surgery, describe OBEs in which they see or hear events or objects outside their sensory range (for instance, Pam Reynolds reported experiencing an OBE during brain surgery and described a surgical instrument she had not seen previously, as well as conversation that occurred while she was under anethesia).