The global population experiencing homelessness has increased significantly over the last century. In 2021, the UN recognised homelessness as a violation of human rights, and urged member states to improve data collection and implement solutions for homelessness. This call presents both a challenge and an opportunity for demographers, especially in the US, to enhance their methodologies for counting and characterising this vulnerable population. Despite the escalating humanitarian crisis, the formal demographic literature engages little with the core demography of individuals experiencing homelessness, focusing instead on the social and behavioural aspects of the issue. A comprehensive review of this literature has identified only one article dedicated to measuring and enumerating people experiencing homelessness. Meanwhile, other disciplines are filling this gap, highlighting the need for demographic expertise on this issue. This article examines the definition and measurement of homelessness in the US, which has been estimated to affect over 770,000 individuals in 2024. It also discusses the demographic methods that can be used to study this population, and concludes with recommendations for the field.