C40 Cities

About C40

Powering global climate action through the collective strength of cities.

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.

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:

1. Help the world halt climate breakdown by halving fossil fuel use by 2030. 

2. Increase resilience so cities and people are protected as they face the impacts of climate breakdown. 

3. Ensure a transition to a clean, green world that is fair, inclusive, and addresses the injustices of climate breakdown.

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.

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:

• C40 Accelerators: 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.

• Programmes and networks: 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.

• Research and knowledge: 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.

• Campaigns and mobilisation: 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.

• Influencing the global agenda: 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.