Homelessness affects less than 1% of the population across the OECD, but nevertheless concerns more than 1.9 million people – and this is likely an underestimate. Homelessness is, nevertheless, difficult to measure and compare across countries. There is no common definition of homelessness, and countries’ data collection efforts differ in their method, scope and frequency. Moreover, people experience homelessness in different ways: the chronically homeless are a small but visible group, who generally require multiple supports, while a large and in some countries growing number of people are temporarily homeless who may also need different types of support. In many countries, homelessness has become increasingly prevalent among women, families with children, youth, migrants and seniors. Some OECD countries have developed national homelessness strategies that call for tailored solutions to address the varied needs of a diverse homeless population. In addition to preventive measures, ‘Housing First’ approaches that provide immediate, permanent housing to the homeless, along with integrated service delivery, may be most effective for the chronically homeless. Emergency support, including rapid rehousing, can help the transitionally homeless.