Unconscious, in psychology, hypothetical region of the mind containing wishes, memories, fears, feelings, and ideas that are not in conscious awareness. They may manifest themselves instead by subtle influences on conscious processes, most strikingly by phenomena such as dreams or neurotic symptoms. Not all mental activity of which the subject is unaware is unconscious; for example, thoughts that may be made conscious by a new focusing of attention are termed foreconscious or preconscious.

The concept of the unconscious may be assumed to have existed as far back as ancient Egypt. Preoccupation with dream interpretation was common, as it was in many early societies. Unconscious processes are believed to underlie shamanic magic and traditional methods of divination and healing. In the late 18th century this was seen in the work in hypnosis carried out by Franz Mesmer.

Modern concepts were developed from 1895 by Sigmund Freud, who theorized that the unconscious consisted of feelings experienced during infantile life, including both instinctual drives (libido) and their modifications by the development of the part of the mind that inhibits those drives (superego). In addition to this, according to the Swiss psychoanalyst Carl Jung, the unconscious also consists of inherited stereotypes belonging to the collective unconscious common to all people.