C40 is a network of more than 80 of the world’s largest cities, committed to collaborating to address climate change through urban action. It aims to reduce greenhouse gas emissions and climate risks while increasing the wealth and wellbeing of urban residents. In the ten years of the network's existence, C40 cities have taken 10,000 climate actions, and they aim to reduce emissions by 3 gigatons of CO2e by 2020.

The sixth biennial C40 Mayors Summit will be held in Mexico City, hosted by Mexico City Mayor Miguel Ángel Mancera and led by the C40 Chair, Rio de Janeiro Mayor Eduardo Paes, who said:
… mayors and cities are essential to achieving the ambition of the Paris Agreement, and C40 cities – representing more than 600 million people and 25% of global GDP – have a particularly important role to play.
The summit will include a number of roundtable discussions and working sessions on city-driven climate actions and projected impacts. Delegates will also share expertise and success stories on a range of different project areas, from low carbon transport to climate resilience.
Find more information on the event website.