Housing First is a policy that offers unconditional, permanent housing as quickly as possible to homeless people, and other supportive services afterward. It was first discussed in the 1990s, and in the following decades became government policy in certain locations within the Western world. There is a substantial base of evidence showing that Housing First is both an effective solution to homelessness and a form of cost savings, as it also reduces the use of public services like hospitals, jails, and emergency shelters. Cities like Helsinki and Vienna in Europe have seen dramatic reductions in homelessness due to the adaptation of Housing First policies, as have the North American cities Columbus, Ohio, Salt Lake City, Utah, and Medicine Hat, Alberta.

Homelessness or houselessness – also known as a state of being unhoused or unsheltered – is the condition of lacking stable, safe, and functional housing. The general category includes disparate situations, such as living on the streets, moving between temporary accommodation such as family or friends, living in boarding houses with no security of tenure, and people who leave their domiciles because of civil conflict and are refugees within their country.