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.

Partnerships unlock action.

C40's network of cities fosters critical partnerships among cities and creates bridges to philanthropic and multilateral organizations.

Shirley Rodrigues, Director, Climate Change, at London-based philanthropic organisation Children's Investment Fund Foundation (CIFF) speaks to C40’s committed mayors who are seeking to implement and share best practice and feasible solutions to tackling climate change around the world.

Meet the 75 C40 cities whose actions – and potential to take further action – have attracted the attention of philanthropies like CIFF.

10 Years of Results

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The last ten years have positioned C40 Cities to lead the world into a better, more sustainable future.

In 2005, then Mayor of London Ken Livingstone convened representatives from 18 megacities to pursue action and cooperation to reduce greenhouse gas emissions. The meeting resulted in the creation of C40. At the time, a small number of leading mayors were working in isolation to make their cities more sustainable. Today, the world’s largest and most important cities are collaborating through C40 to drive climate action through idea sharing, and by doing so, are leading the climate agenda on a global scale toward lower emissions and greater resilience. 

Each month during 2015, C40 will celebrate by looking back on the last decade of results and highlighting the many accomplishments of its member cities:

Join us as we build on the successes of the past 10 years to forge a brighter future, and stay up to date on the #RoadToParis by following us on Twitter, liking us on Facebook, and connecting with us on LinkedIn