What makes a community successful? One important measure is how well it meets the needs of its citizens in all stages of their lives. Is it safe? Affordable? Walkable? Healthy? Inclusive? Is it a great place to grow up and grow old? In short, is it "age-friendly?" In many communities large and small across America and around the globe, the answer is still no. This is unfortunate because, from Athens, Georgia to Athens, Greece, individuals are living longer and the world's population is getting older, quickly and permanently. This longevity is a wonderful, hopeful phenomenon with many positive ramifications. At the same time, it poses a challenge to cities, towns, and neighborhoods, many of which are still unprepared to serve -- or benefit from -- the fast-growing number of older citizens. The good news is that communities still have time to seize the dynamic opportunity that an aging population can present. In fact, many thought leaders now believe that the communities that fare best in the 21st century will be those that both tackle the challenges and embrace the positive possibilities that an aging population creates. Grantmakers In Aging (GIA) has developed this publication as part of Community AGEnda: Improving America for All Ages, an initiative funded by the Pfizer Foundation. The document's purpose is to introduce private philanthropies and local, state, and federal funders to this new, transformative way of thinking about aging and community development. In it, we survey the current state of the age-friendly community movement, showcase notable examples, and demonstrate how urban, suburban, exurban, and rural communities can get started or advance their work. A searchable database of age-friendly programs across America, a curated collection of implementation tools, and other resources are also available at GIAging.org/CommunityAGEnda for any funder, planner, nonprofit, government agency, or citizen seeking to work toward a more age-friendly future.