Unregulated opioids remain a leading driver of preventable mortality and potential years of life lost in Canada. Emergency departments (EDs)-open 24/7 and frequently accessed by people who use drugs-offer critical opportunities to reverse toxicity, mitigate harm, and initiate treatment. Yet, high quality evidence to guide ED care for patients with opioid poisoning and concomitant opioid dependence or opioid use disorder is limited. The investigators aim to establish a pan Canadian registry of patients presenting to EDs with opioid poisoning to generate timely, practice informing evidence. The investigators will create the Canadian Emergency Department Research Network (CEDRN) Opioid Registry across participating EDs nationwide. Using automated screening of electronic health records (EHRs), the investigators will identify consecutive patients of all ages with suspected or confirmed opioid poisoning at their index ED visit. The project's objectives are to establish a pan-Canadian registry of Emergency Department patients presenting with opioid poisoning, harmonize data collection across participating sites, describe variations in patient characteristics, clinical practice and outcomes, and derive a clinical decision rule to predict the risk of dying within 60 days. The expected outcomes include advancing healthcare delivery, improving patient and provider experiences, and enhancing population health and health system sustainability for individuals with opioid poisoning. This research is crucial for addressing the opioid crisis in Canada and has the potential to significantly impact patient care and outcomes.