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.

City mayors are the key to a sustainable future

Mark Watts, Executive Director of C40, speaking at the recent Environmental Industries Commission annual conference:

“The solutions to big problems like climate change are going to be delivered in cities and often by city leaders as much as by national leaders." 

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.