A trauma trigger is a psychological stimulus that prompts involuntary recall of a previous traumatic experience. The stimulus itself need not be frightening or traumatic and may be only indirectly or superficially reminiscent of an earlier traumatic incident, such as a scent or a piece of clothing. Triggers can be subtle and difficult to anticipate. A trauma trigger may also be called a trauma stimulus, a trauma stressor or a trauma reminder.

The process of connecting a traumatic experience to a trauma trigger is called traumatic coupling. When trauma is "triggered", the involuntary response goes far beyond feeling uncomfortable and can feel overwhelming and uncontrollable, such as a panic attack or a strong impulse to flee to a safe place. Avoiding a trauma trigger, and therefore the potentially extreme reaction it provokes, is a common behavioral symptom of posttraumatic stress disorder (PTSD), a treatable and usually temporary condition in which people sometimes experience overwhelming emotional or physical symptoms when something reminds them of, or "triggers" the memory of, a traumatic event. Long-term avoidance of triggers increases the likelihood that the affected person will develop a disabling level of PTSD. Identifying and addressing trauma triggers is an important part of treating PTSD.

A trigger warning is a message presented to an audience about the contents of a piece of media, to warn them that it contains potentially distressing content.