Scheduled for November 11 to 14 2021, it will feature 40 kilometre and 80km races, close to the distances of a marathon and a double marathon, which are 42.1km and 84.2km respectively.

There will also be classic mountain running races for seniors and juniors as well as a vertical uphill race.

This new Championship has been organised by the World Mountain Running Association (WMRA), the International Association of Ultrarunners (IAU) and the International Trail Running Association (ITRA), with support from World Athletics.

"We encourage runners of all kinds to explore everything our sport has to offer," said World Athletics President Sebastian Coe.

In the north of Thailand, Chiang Mai is one of the nation's biggest tourist spots.

This competition replaces the separate World Championships that were previously held by the WMRA and the IAU and ITRA.

The amalgamation was created to attract the best trail and mountain runners, as well as provide more opportunity for mass participation racing.

"I am delighted that the Tourism Authority of Thailand under the Ministry of Tourism Sport is ready to support and to be a part of the first edition of the World Mountain and Trail Running Championships," said Minister of Tourism and Sport of Thailand, Pipat Ratchakitprakarn.

"We are looking forward to being able to host athletics and countries from all over the world for what we believe will be a special event that will showcase the best of Chiang Mai and mountain and trail running, I would like to thank you for giving us this opportunity to host such a new and exciting world class event."

A 40km trail race and the vertical uphill race are set to take place on the Friday, with the 80km trail race following on Saturday.

The senior and junior mountain races will conclude the Championships on Sunday.

Jonathan Wyatt, Nadeem Khan and Bob Crowley, the Presidents of the WMRA, IAU and ITRA released a joint statement.

"We are delighted to be able to end such a difficult year with the announcement of our first-ever joint World Mountain and Trail Running Championships," they said.

"Chiang Mai has a growing reputation for hosting quality off-road running events, and we are sure it will provide excellent courses to enable the best runners to test themselves against one another."