World Mayors Summit 2025

Mayors, governors, and local leaders will meet in Rio de Janeiro, Brazil, between 3-5 November, to align on climate action, finance, and just transition, ensuring cities are at the centre of the global agenda.

Explore our cities
C40 has 97 member cities
Making up more than 22% of the global economy1

Accelerator Reports

Latest Reports Now Available

Since 2017, 74 forward-thinking C40 cities have been driving transformative action in critical sectors through C40’s High-Impact Accelerators.

In the latest Accelerator Reports, we celebrate the progress and impact of cities’ climate actions.

© Laure Rees-Smith – C40

Sources:
1. Oxford Economics data + C40 modelling and World Bank for global GDP.