This paper was prepared in support of Japan’s G20 Presidency. It takes stock of ongoing and projected population ageing across G20 economies and its far-reaching implications for economic growth, productivity, inequality within and between generations and the sustainability of public finances. Rising old-age dependency ratios will put the financing of adequate pensions, health and long-term care under high pressure. The paper provides recommendations on policy responses to address ageing-related challenges and highlights good practices. A comprehensive approach is needed, tailored to each country’s institutional and policy settings and social preferences, and may span many areas of public policy: improving the design of public pensions, incentivising private savings, enhancing the efficiency of health care provision, expanding the coverage of social security systems, promoting employability and skills of older workers, and striving for a better labour market inclusion of women, youth and migrants.