Primal therapy (also known as primal scream therapy) is a trauma-based psychotherapy created by Arthur Janov during the 1960s, who argued that neurosis is caused by the repressed pain of childhood trauma. Janov argued that repressed pain can be sequentially brought to conscious awareness for resolution through re-experiencing specific incidents and fully expressing the resulting pain during therapy. Primal therapy was developed as a means of eliciting the repressed pain; the term Pain is capitalized in discussions of primal therapy when referring to any repressed emotional distress and its purported long-lasting psychological effects. Janov believed that talking therapies deal primarily with the cerebral cortex and higher-reasoning areas and do not access the source of Pain within the more basic parts of the central nervous system.

The phrase “Primal Scream Therapy” is something of a misnomer and is often used misleadingly by journalists, critics and even some therapeutic imitators. A scream or screaming “may” occur during the therapeutic process but it is not an essential part of the journey nor is it the goal. Clients are extremely unlikely to access early pain by just screaming. The process is better thought of as a felt journey, starting in the present and following the trail of pain back into early childhood pain. It has been described as like peeling an onion, layer by layer. There are no shortcuts.

Primal therapy is used to re-experience childhood pain—i.e., felt rather than conceptual memories—in an attempt to resolve the pain through complete processing and integration, becoming real. An intended objective of the therapy is to lessen or eliminate the hold early trauma exerts on adult behaviour.

Primal therapy became very influential during a brief period in the early 1970s after the publication of Janov's first book, The Primal Scream. It inspired hundreds of spin-off clinics worldwide and served as an inspiration for many popular cultural icons. Singer-songwriter John Lennon, actor James Earl Jones, and pianist Roger Williams were prominent advocates of primal therapy. Primal therapy has since declined in popularity. However, proponents of the methodology continue to advocate and practice the therapy or variations of it.

Primal therapy is not accepted in the field of psychology. Psychologists have criticized its lack of controlled outcome trials which would demonstrate effectiveness. Nevertheless, Janov continued to advocate the therapy up until his death in 2017, and primal therapy is still practiced by a few clinicians worldwide.

Janov stated that neurosis is the result of suppressed pain, which is the result of trauma, usually trauma of childhood origin. According to Janov, the only way to reverse neurosis is for the neurotic to recall their trauma in a therapeutic setting. Janov contended that the neurotic can thereby re-experience their feelings in response to the original traumatic incidents but can now express the emotions that at that time were repressed, thereby resolving the trauma.

Janov believed that there is only one source of mental illness (besides genetic defects): imprinted pain. He argued that this unitary source of neurosis implies that there can be only one effective cure: re-experiencing.

In primal theory, "Primal Pain is deprivation or injury which threatens the developing child. A parent's warning is not necessarily a Primal Pain for the child. Utter humiliation is... An infant left to cry it out in the crib is in Pain... It is not hurt as such which defines Primal Pain but rather the context of the hurt or its meaning to the impressionable developing consciousness of the child."