We are a global network of mayors driving the future of city climate action
96 cities representing 920 million people. 23% of the world’s economy.1
We help cities move faster and go further on climate through:
- sector programmes that turn ambition into results
- accelerators that speed innovation and delivery
- research that powers evidence-based action
- finance pathways that unlock the resources to act
- global advocacy that shapes policy and raises ambition
Founded in 2005 by 18 pioneering cities, C40 now leads global progress on climate.
Mobilising cities around three urgent missions
C40 cities are protecting the people and places we love by uniting behind three major priorities:
- Help the world halt climate breakdown by halving fossil fuel use by 2030.
- Increase resilience so cities and people are protected as they face the impacts of climate breakdown.
- Ensure a transition to a clean, green world that is fair, inclusive, and addresses the injustices of climate breakdown.
Accountability built into every commitment
Every member city commits to the C40 Leadership Standards. These performance-based requirements ensure that ambition translates into action and progress stays on track across the whole network.
Leadership that reflects every region and reality
C40’s collective vision is driven by mayors of its members cities.
C40 Cities UK’s direction is shaped by a Steering Committee of mayors representing cities from all C40’s regions and is co-chaired by leaders from the Global South and Global North. Together with C40 UK’s Board of Directors, they provide strategic oversight.
The C40 Cities US Board of Directors provides strategic oversight of C40 activity in the US.
Meet our leadership
From the Global South and North, C40’s Co-Chairs set the vision and champion mayors’ collective power.
Strategic oversight meets accountability. Our Board unites global leaders to strengthen city-led climate action.
14 mayors from every region form C40’s Steering Committee, setting priorities and guiding the network’s global direction.
How we help cities move forward, faster
C40 helps cities move with urgency and confidence, backing ambition with the expertise, evidence, and funding to make it a reality.
Our focus areas
Cities make public commitments to take proven climate action by 2030 and hold each other accountable. With expert guidance and peer support, cities set ambitious targets, report on progress, and demonstrate what works.
Peer-to-peer collaboration drives better, faster progress. City officials swap experience on clean transport, buildings, waste, and more, turning shared knowledge into stronger climate action.
C40’s research and knowledge gives cities the evidence they need to act, combining data, policy analysis, and on-the-ground insight to shape smarter climate decisions.
C40 raises awareness and educates about city climate action, amplifies frontline voices, and mobilises at every level, from local to global, through storytelling, education, and strategic campaigns.
C40 brings mayors’ voices into global climate negotiations, at the likes of COP and G20, showing world leaders how city action drives real progress.
Backed by those who believe in city climate leadership
C40 partners with governments, foundations, and businesses that share a belief that cities are where climate solutions happen.
This collaborative approach has helped C40 cities cut emissions five times faster than the global average, reduce air pollution by 8%, and create over 21 million good green jobs. It’s a model that recognises cities as central climate actors and backs them with the resources and support they need to lead.
Every contribution strengthens the network. Funding, expertise, access, and support help us respond quickly, scale what works, and ensure that climate action benefits everyone.
Annual reports
Read through C40’s annual reports, where you’ll find results on emissions, clean air, green jobs, and resilience. Discover plenty of examples of how cities are beating targets, driving real progress, and proving the power of local climate action.
Our people and values
Diverse in background but connected in purpose, we work as one global network focused on inclusion, collaboration, and impact.
Our teams put those values into practice across regional hubs in London, New York, and Johannesburg, and other offices across the world.
Our policies ensure those principles embed transparency, fairness, and respect in everything we do.
Get the latest climate action updates straight to your inbox
- Figures are approximate and relate to people living and working in the wider city, based on the latest available data, 2024, from city GPC inventories, Oxford Economics “Global Cities” dataset and global GDP data from The World Bank. ↩︎