Homelessness is a major social problem in the United States. The article starts with an overview of homelessness in American history, followed by the definition of contemporary homelessness, its prevalence, and the composition and diverse characteristics of the homeless population. Contrasting perspectives on what causes homelessness are discussed, while the multidimensionality of the homeless experience is explored. The unique experiences of three subpopulations, including homeless persons who are involved in criminal justice, emerging youth leaving foster care, and older homeless persons are further featured. Public and community responses to homelessness are examined, highlighting evidence-based and emerging practices that aim at reducing and preventing homelessness. A discussion of international homelessness follows, as homelessness is recognized as a global issue affecting people living in poverty in both the developed and developing world. The article concludes with discussion of the implications for social work.