Exposure to trauma is pervasive in societies worldwide and is associated with substantial costs to the individual and society, making it a significant global public health concern. We present evidence for trauma as a public health issue by highlighting the role of characteristics operating at multiple levels of influence - individual, relationship, community, and society - as explanatory factors in both the occurrence of trauma and its sequelae. Within the context of this multi-level framework, we highlight targets for prevention of trauma and its downstream consequences and provide examples of where public health approaches to prevention have met with success. Finally, we describe the essential role of public health policies in addressing trauma as a global public health issue, including key challenges for global mental health and next steps for developing and implementing a trauma-informed public health policy agenda. A public health framework is critical for understanding risk and protective factors for trauma and its aftermath operating at multiple levels of influence and generating opportunities for prevention.