This special issue of Addiction Science & Clinical Practice, “Addiction treatment access and utilization among criminal justice involved populations”, presents a series of articles on substance use disorder treatment access and utilization by people who have contact with the criminal justice system (e.g., jails, prisons, and courts). Despite the high prevalence of substance use disorders among people who experience these settings, evidence-based treatment for substance use disorders may be unavailable and/or care may be fragmented during transitions between settings. Articles in this special issue address several gaps in the literature and present a conceptual model of opioid overdose risk, the results of a randomized controlled trial to increase treatment uptake and retention during and after incarceration, descriptions of barriers to treatment after release from incarceration, and data from nationally representative surveys of substance use disorders and treatment use among people who have been involved in the criminal justice system. Importantly, the voices of people with lived experience in the criminal justice system were incorporated in two manuscripts. Together these articles advance our understanding of how to improve care coordination and expansion of services across systems and organizations to prevent overdose, improve treatment utilization, and ultimately, improve health outcomes among criminal justice involved populations in the United States who have substance use disorders or use substances.