Objective: To estimate the economic burden of posttraumatic stress disorder (PTSD) in the United States civilian and military populations from a societal perspective.Methods: A prevalence-based and human capital approach was used to estimate the total excess costs of PTSD in 2018 from insurance claims data, academic literature, and governmental publications. Excess direct health care costs (pharmacy, medical), direct non-health care costs (research and training, substance use, psychotherapy, homelessness, disability), and indirect costs (unemployment, productivity loss, caregiving, premature mortality) associated with PTSD were compared between adults with PTSD and adults without PTSD, or the general population if information was not available for adults without PTSD.Results: The total excess economic burden of PTSD in the US was estimated at $232.2 billion for 2018 ($19,630 per individual with PTSD). Total excess costs were $189.5 billion (81.6%) in the civilian population and $42.7 billion (18.4%) in the military population, corresponding to $18,640 and $25,684 per individual with PTSD in the civilian and military populations, respectively. In the civilian population, the excess burden was driven by direct health care ($66.0 billion) and unemployment ($42.7 billion) costs. In the military population, the excess burden was driven by disability ($17.8 billion) and direct health care ($10.1 billion) costs.Conclusions: The economic burden of PTSD goes beyond direct health care costs and has been found to rival costs for other costly mental health conditions. Increased awareness of PTSD, development of more effective therapies, and expansion of evidence-based interventions may be warranted to reduce the large clinical and economic burden of PTSD.