Sadiq Khan is set to make a 12,000-mile round trip to Brazil to host a climate change conference.
The London mayor will make a trip to Rio in November for the 2025 C40 World Mayors Summit, due to take place at COP 30.
He is co-chair of C40, a network of almost 100 city mayors from across the world trying to reduce global warming and halve emissions by 2030.
Sir Sadiq has already made more than 20 foreign trips in the nine years that he's been mayor since 2016 - including a trip to Paris in the last few days to meet other mayors from the group.
He is also due to visit Nigeria, Ghana and South Africa this summer after announcing last December that he would become the first London Mayor to lead a trade delegation to Africa.
