The increasing proportion of persons living alone has come to be emblematic in many ways of modern Western societies because it represents the importance conceded to the individual and to individual goals at the expense, basically, of the family. Solo living has been interpreted within the context of changing values and preferences, changing personal and conjugal realities, and the changing work contexts so often associated with the Second Demographic Transition. We know little about patterns and trends in living alone over the life course in much of the world because most research to date has concentrated on regional and national portrayals or on living arrangements in later life. This study provides a systematic look at the differences in living alone by age and sex in 113 countries. Our aim is to understand the extent to which behavior differs around the world and the implications this has for society. We also examine the relationship between trends in living alone and levels of human development. Results are taken from three massive datasets: census and survey microdata from IPUMS-international, Demographic Health Surveys, and EU-Labor Force Surveys.