Complex post-traumatic stress disorder (CPTSD, cPTSD, or hyphenated C-PTSD) is a stress-related mental disorder generally occurring in response to complex traumas (i.e., commonly prolonged or repetitive exposure to a traumatic event (or traumatic events), from which one sees little or no chance to escape).

In the ICD-11 classification, C-PTSD is a category of post-traumatic stress disorder (PTSD) with three additional clusters of significant symptoms: emotional dysregulation, negative self-beliefs (e.g., shame, guilt, failure for wrong reasons), and interpersonal difficulties. C-PTSD's symptoms include prolonged feelings of terror, worthlessness, helplessness, distortions in identity or sense of self, and hypervigilance. Although early descriptions of C-PTSD specified the type of trauma (i.e., prolonged, repetitive), in the ICD-11 there is no requirement of a specific trauma type.

The World Health Organization (WHO)'s International Statistical Classification of Diseases has included C-PTSD since its eleventh revision that was published in 2018 and came into effect in 2022 (ICD-11). The previous edition (ICD-10) proposed a diagnosis of Enduring Personality Change after Catastrophic Event (EPCACE), which was an ancestor of C-PTSD. Healthdirect Australia (HDA) and the British National Health Service (NHS) have also acknowledged C-PTSD as mental disorder. The American Psychiatric Association (APA) has not included C-PTSD in the Diagnostic and Statistical Manual of Mental Disorders. The related disorder, Disorders of Extreme Stress – not otherwise specified (DESNOS) was studied for inclusion in the DSM-IV, but not ultimately included. Instead, the symptoms of PTSD were expanded in the DSM-IV and then DSM-V to better capture the range of symptoms that can follow from all types of trauma.

The diagnosis of PTSD was originally given to adults who had suffered because of a trauma (e.g., during a war, rape). However, the situation for many children is quite different. Children can suffer chronic trauma such as maltreatment, family violence, school bullying, dysfunction, or a disruption in attachment to their primary caregiver. In many cases, it is the child's caregiver who causes the trauma. The diagnosis of PTSD does not take into account how the developmental stages of children may affect their symptoms and how trauma can affect a child's development.

The term developmental trauma disorder (DTD) has been proposed as the childhood equivalent of C-PTSD. This developmental form of trauma places children at risk for developing psychiatric and medical disorders. Bessel van der Kolk explains DTD as numerous encounters with interpersonal trauma such as physical assault, sexual assault, violence or death. It can also be brought on by subjective events such as abandonment, betrayal, defeat or shame.

Repeated traumatization during childhood leads to symptoms that differ from those described for PTSD. Cook and others describe symptoms and behavioral characteristics in seven domains:

Adults with C-PTSD have sometimes experienced prolonged interpersonal traumatization beginning in childhood, rather than, or as well as, in adulthood. These early injuries interrupt the development of a robust sense of self and of others. Because physical and emotional pain or neglect was often inflicted by attachment figures such as caregivers or other siblings, these individuals may develop a sense that they are fundamentally flawed and that others cannot be relied upon.

A 2025 systematic review and meta-analysis reported that the pooled prevalence rates for ICD-11 PTSD and complex PTSD were 2% and 4%, respectively, among adults in non-war-exposed/economically developed countries/regions; they increased to 16% and 15%, respectively, in war-exposed/less economically developed countries/regions.