This guide equips advocates and other changemakers with critical information for advancing health equity in behavioral health care, including background on financing and delivery of behavioral health services, an overview of major challenges and inequities in access to and quality of mental health and substance use services, and a summary of policy opportunities for advancing equity. It covers the following topics:behavioral health system overview key population characteristics providers and service delivery financing details barriers to access, quality, and equitable outcomes disparities primary oversight entities and accountability mechanisms policies and actions to reduce barriers and disparities a vignette illustrating challenges in getting behavioral health care additional resources and a glossary This guide is part of a larger project on inequities and policy levers in the US health care system. For the complete guide, visit https://www.urban.org/projects/guide-equity-us-health-care-system.