The increase in human longevity is a major achievement, which brings individual well-being and strong contributions to society, but population ageing also generates challenges. This paper documents demographic trends in OECD countries, highlighting that ageing today largely reflects past fertility, longevity, and migration developments. Policies have moderate or delayed impacts on population ageing, hence they should also focus on adapting to ongoing demographic trends. The paper quantifies ageing’s potential impacts on labour supply and GDP per capita, showing that the extension of working lives as longevity rises could mitigate, but not completely offset, the negative effects of ageing on employment. It also examines how ageing may affect productivity through various micro and macroeconomic mechanisms. Finally, it provides policy directions for addressing the ageing challenge, through supporting healthy ageing, boosting employment, job quality and labour mobility in all age groups, and promoting older workers’ productivity by further developing lifelong learning and fostering an age-friendly management culture.