There is considerable overlap between the homeless and correctional populations in the United States. Individuals with a history of criminal justice contact are overrepresented among the homeless and those who have recently been homeless are disproportionately concentrated among correctional populations. Such overlap is in part due to shared risk factors. Poor, low skill, men of color, and individuals with mental illness and substance abuse and dependency issues are concentrated among the homeless and incarcerated. Said marginalized persons end up in correctional facilities, shelters, and the streets primarily because of two large-scale American policies: (1) the criminalization of homelessness and (2) mass incarceration and its detrimental consequences. Concerning the former, homeless individuals typically enter the criminal justice system for minor offenses that are often the direct result of being homeless (e.g., public disorder or petty theft). Yet because they are often unable to afford an attorney or bail and have no place to go if released, homeless individuals frequently remain in jail longer than individuals with stable housing, and over time they accrue lengthy criminal histories. Notably, such practices are not new; homelessness has long been criminalized. For instance, in colonial America, the homeless were sent to poor houses, which in many cases resembled modern prisons. Today, an emerging literature suggests that mass incarceration may contribute to homelessness. Indeed, the time trends overlap: contemporary homelessness grew in tandem with incarceration, beginning in the early 1980s. Over 641,000 individuals exit prison annually, of which a portion become homeless. Obtaining stable housing is not only indicative of successful reintegration, but other forms of reintegration such as employment are often dependent on having stable housing. Furthermore, homelessness is associated with recidivism. Reintegration challenges combined with the consequences of incarceration and the concentration of standard correlates of homelessness in this population help explain why individuals leaving prison are at an elevated risk. The data challenges for studying homeless and justice-involved populations are considerable. Without a permanent address, these highly mobile individuals are missing from many traditional forms of data used by social scientists such as household surveys. As a result, much of the work on this topic is theoretical in nature. Empirical assessments rely heavily on administrative data, such as correctional and emergency shelter records, and ethnographic work. Overall, much work remains to be done to understand the pathways between homelessness and the criminal justice system. Nonetheless, homelessness is a form of severe social exclusion and when combined with the stigma of incarceration, individuals may be doubly disadvantaged. Indeed, individuals with a history of prison or jail spells are among the most disadvantaged homeless, experiencing lengthy and/or repeated homelessness. However, the overlap between homelessness and the criminal justice system can be effectively reduced. Indeed, access to affordable housing saves taxpayer money while maintaining public safety.