The relationship between trauma and addiction is inextricably intertwined, well established and known (De Bellis and Zisk, Child Adolesc Psychiatr Clin N Am 23(2):185–222, 2014; Broekhof et al., Addict Behav Rep 17:100488, 2023). The reasons for this are profoundly simple yet considerably complex: trauma in all its forms changes the brain and, as such, impacts an individual’s thoughts, actions, behaviors, and motivations. As a result, individuals with a history of trauma, no matter how it is defined, are particularly vulnerable to developing addictive behaviors. This chapter will explore how trauma is (and is not) defined, the prevalence of trauma in modern society, the impact trauma has on our body, and strategies for providing trauma-informed care in a trauma-responsive environment.