This report defines Housing First services as: support for homeless people that closely reflects the core principles and operational practice of the model originally developed by Dr Sam Tsem-beris and Pathways to Housing in the USA. Housing First is an intensive support model centred on enabling homeless people with high and complex needs to live in their own independent homes, exercising a very high degree of control over the nature of the support they receive. Housing First is distinct from rapid rehousing and housing-led services, which also aim to house people rapidly but are low intensity services intended for homeless people with low support needs, or whose needs can be largely, or entirely, addressed by the provision of an adequate, affordable and secure home.