Asia and the Pacific, home to more than 60 per cent of the world's population, is undergoing a profound demographic transition. The region's population is projected to peck at 5.1 billion by the early 2050s before declining, while shifting age structures present both significant challenges and opportunities for sustainable development. This study, prepared for the eighty-second session of the Economic and Social Commission for Asia and the Pacific, examines the economic and social implications of rapid demographic change, providing a comprehensive framework for advancing a society for all ages. The study analyses the demographic transition affecting all countries, where some are experiencing rapid population ageing while others have large youth populations. it addresses a policy challenge: how to create decent jobs, enhance intelligence. The publication explores the future of work across the life course, active and healthy ageing, and women's economic empowerment, while examining pathways to strengthen the care economy as a public good. Drawing on regional evidence and disaggregated data, the study presents action-oriented and scalable policy recommendations that call for rethinking economic and social systems so that people of all ages can contribute to and benefit from sustainable development. These recommendations emphasize strengthening intergenerational equity, expanding lifelong learning and reskilling opportunities, promoting age-friendly workplaces and supporting women's full and decent participation in the labour market. This publication offers timely guidance for policymakers, practitioners and stakeholders committed to building inclusive, equitable and sustainable societies for present and future generations, ensuring that no one is left behind.