This paper, prepared jointly by the five regional commissions of the United Nations, explores the social and economic challenges and opportunities of demographic shifts towards multigenerational societies across the countries covered by the five regional commissions. It discusses the latest evidence on demographic trends and intergenerational relations, labour markets, social protection, care, living arrangements and digitalization across regions, and it provides recommendations to build societies for all ages. With a strong interdisciplinary and interregional focus, the paper addresses intergenerational relations from a variety of perspectives and highlights common actions required, while also acknowledging regional differences.