Crisis services have been undergoing a rapid expansion of growth that has been catalyzed since the release of the 2020 National Guidelines for Behavioral Health Crisis Care Best Practice Toolkit and the transition of the National Suicide Prevention Lifeline to the 988 Suicide & Crisis Lifeline (988 Lifeline). In light of this expansion, communities have been designing crisis systems to meet their specific needs, which has created widespread variability in the landscape of crisis care. In order to coalesce and optimize alignment of this burgeoning field while supporting expansion and sustainability in a manner whereby crisis care will continue to meet the unique needs of communities, this Model Definitions for Behavioral Health Emergency, Crisis, and Crisis-Related Services (Model Definitions) document was developed. The content of this document, through the development of more uniform definitions, seeks to promote service quality and consistency, and further payer adoption of emergency, crisis, and crisis-related behavioral health services. Achieving these goals will support increased access to quality, equitable emergency, and crisis care for all individuals