By 2050, 20% of the world's population will be over the age of 65 years, with projections that 80% of older adults will be living in low- to middle-income countries. Physical inactivity and sedentary time are particularly high in older adults, presenting unique public health challenges. In this article, we first review evidence that points to multiple beneficial outcomes of active aging, including better physical function, cognitive function, mental health, social health, and sleep and suggest the need to shift the research focus from chronic disease outcomes to more relevant outcomes that affect independence and quality of life. Second, we review the critical role of age-friendly environments in facilitating active aging equitably across different countries and cultures. Finally, we consider emerging opportunities related to social engagement and technology-enabled mobility that can facilitate active aging. In all these contexts, it is a priority to understand and address diversity within the global aging population. Expected final online publication date for the Annual Review of Public Health, Volume 43 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.