In response to increasing life expectancies and urbanization, initiatives for age-friendly cities seek to facilitate active and healthy aging by strengthening supports and services for older people. While laudable, these efforts typically neglect early-life exposures that influence long-term well-being. With a focus on the urban physical environment, we argue that longevity-ready cities can accomplish more than initiatives focused solely on old age. We review features of cities that cumulatively influence healthy aging and longevity, discuss the need for proactive interventions in a changing climate, and highlight inequities in the ambient physical environment, especially those encountered at early ages, that powerfully contribute to disparities in later life stages. Compared with strategies aimed largely at accommodating older populations, longevity-ready cities would aim to reduce the sources of disadvantages across the life course and simultaneously improve the well-being of older people.