Cities are leading the way
The C40 World Mayors Summit 2025, co-hosted by the Mayor of London and C40 Cities Co-Chair Sadiq Khan and the Mayor of Rio de Janeiro Eduardo Paes, brings together mayors from nearly 100 C40 cities, alongside business leaders, philanthropists, investors, academics, and civil society.
This year’s Summit will kick off the COP30 Local Leaders Forum, co-hosted by Bloomberg Philanthropies and the COP30 Presidency. The Forum puts local leadership at the heart of global negotiations, showcasing scalable city-led solutions and ensuring local priorities shape the outcomes of COP30.
Taking place from 3-5 November in Rio de Janeiro, just days before COP30 in Belém, the Summit marks a critical moment for city-led climate action. Building on two decades of C40 Cities leadership, it will showcase innovative solutions from cities worldwide, demonstrate what’s possible through delivery-focused collaboration, and build momentum ahead of COP30.
Cities are already delivering practical, urgent solutions to the climate crisis
The Yearly Offer of Action
To deliver the Decade of Acceleration called for by the United Nations Secretary General, decision-makers need to act now, not in five or ten years.
At the World Mayors Summit 2025, C40 Cities and the Global Covenant of Mayors (GCoM) are showcasing how cities are moving from negotiation to delivery, turning climate pledges into real-world progress.
The Yearly Offer of Action sets out what cities have achieved, what comes next, and how we’re accelerating delivery year after year until climate breakdown is under control.
News & Announcements
Local Leaders Awards
As part of the Summit, the Bloomberg Philanthropies Local Leaders Awards will honour city and regional governments delivering standout climate action. The Awards will recognise one Brazilian and one global leader across key COP30 priority areas:
- Multilevel partnerships
- Just energy transition
- Adaptation and resilience
- Health and well-being
Sponsors
The C40 World Mayors Summit is presented as part of the COP30 Local Leaders Forum, co-hosted by the COP30 Presidency and Bloomberg Philanthropies:
With additional support from:
