This article aims to characterise hospital admissions involving opioid toxicity across South Australia to guide future implementation and evaluation of risk mitigation strategies. International Classification of Diseases, 10th Edition codes (T40.0-T40.4) were used to identify admissions involving pre-hospital opioid toxicity in public hospitals across South Australia from 1 June 2017 to 30 August 2020. Demographic and episode of care data were extracted and summarised using descriptive statistics. Admission cost estimates were calculated using Independent Hospital Pricing Authority data. A total of 2046 cases met the criteria for inclusion; over half (56%) were female and median age on admission was 44 years (interquartile range 27 years). Where opioid toxicity was the primary diagnosis, 70% of admissions did not specify the responsible opioid and 23% were related to heroin use. One-fifth of admissions occurred outside of metropolitan Adelaide. Individuals living in an area of relative socio-economic disadvantage were over-represented. Over half of admissions required a stay >24 h; 19% were admitted for ≥5 days, 22% required intensive care and ~10% required mechanical ventilation. The total estimated cost of admissions involving opioid toxicity in South Australia over the 3-year period was $18,230,546.50, equating to $5.6 million per annum. These findings highlight the significant personal, fiscal, and systemic impacts of opioid toxicity-related hospital admissions in South Australia and provide a baseline to evaluate the effectiveness of initiatives to reduce opioid-related harm, including real-time prescription monitoring and take-home naloxone supply.