This epic trail running endurance race sees competitors heading 120km from Courmayeur in Italy, heading through Bourg Saint Maurice and on to Chamonix to finish.
It's one of the toughest trail running races there is, with 7250 positive elevation gain along the route.
Runners leave Courmayeur at 07:00 and reach BSM by around midday. The fastest competitors make it to Chamonix that same night, with the slower ones arriving the next day.
Come along to see them and cheer them along.
Read more about the UTMB.