Individuals aged 65 years and older currently make up a larger share of the population than ever before, and this group is predicted to continue growing both in absolute terms and relative to the rest of the population. This chapter begins by introducing the facts, figures, and forecasts surrounding the aging of populations across different countries at varying levels of development. In light of these trends, we examine challenges facing graying societies through the lenses of health, economics, and policy development. The chapter concludes with a selection of adaptable strategies that countries might consider to mitigate the strain – and to harness the full potential – of aging populations worldwide.