This paper provides evidence and insights on the main demographic trends and challenges in cities across OECD countries, with a focus on G7 cities. The paper also draws implications for urban policy and city-specific examples to address the negative effects of demographic change, with a view to building more inclusive, sustainable, and resilient cities. Preliminary findings from the paper served as input to the G7 Ministerial Meeting on Sustainable Urban Development (7-9 July 2023, Takamatsu, Japan) under the G7 Japanese Presidency.