This chapter offers a global perspective on house sharing by tracing its historical development and examining the sociological factors that have contributed to its growing prevalence. It begins by tracing the rise of house sharing in global cities, highlighting how it has shifted from a transitional phase to a long-term or even permanent housing strategy, especially for single adults in urban centres. The chapter unpacks the broader structural conditions that have contributed to this shift, including affordability crises, changing household formations, and the precarity of contemporary urban life. A particular focus is placed on the UK context, with a detailed overview of Houses in Multiple Occupation (HMOs), including legal definitions and statistical data that frame shared housing as a normalised feature of London’s rental landscape. The chapter concludes by critically reviewing existing research on house sharing in major metropolises such as Tokyo, Sydney, New York, and London. Emphasis is placed on studies that adopt micro-level approaches to explore the social aspects of house sharing.