The C40 Cities Climate Leadership Group (C40) is a network of the world’s megacities committed to addressing climate change.

Acting both locally and collaboratively, C40 Cities are having a meaningful global impact in reducing both greenhouse gas emissions and climate risks. C40 brings together a unique set of assets and creates a shared sense of purpose. C40 offers cities an effective forum where they can collaborate, share knowledge and drive meaningful, measurable and sustainable action on climate change.

Explore an interactive list of the C40 Cities and our Networks and Research connecting them.

C40 Cities: Showing the Way Forward

Take a ride with us through five of our cities to see actions and progress.

See the C40 like never before in this short video that takes you on a journey through member cities London, Johannesburg, Jakarta, Rio de Janeiro and New York. 

Meet the C40 Cities taking action.

C40's Thought Leadership

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C40 partners with leading institutions like the World Resources Institute (WRI) and ICLEI - Local Governments for Sustainability (ICLEI) to create knowledge and tools to address urban climate change issues.

C40 acheives results by creating and sharing knowledge. This has been our guiding principle for the past 10 years and continues to inform our work today -- from thematic "good practice" white papers on successful policies and programs, to cutting-edge research on urban watersheds, to the first global standard to measure greenhouse gas emissions from cities. We invite you to explore our latest examples below to learn more about C40's important thought leadership.