Hellfest, also called Hellfest Summer Open Air, is a rock festival focusing on heavy metal music, held annually in June in Clisson, France. Its high attendance makes it the French music festival with the largest audience. It is also one of the biggest metal festivals in Europe and the first to exist in France.

It originated from another music festival, the Fury Fest, held from 2002 to 2005, in different areas of Pays de la Loire. Hellfest took over in 2006 and over the years has seen a continuous rise in visitors, from 22,000 in the first edition, to 55,000 tickets sold per day in 2017. In 2022, the seven-day festival featured 350 bands and was attended by 60,000 people per day.

Its programming is primarily focused on hard rock and metal on the two main stages, while each of the four other festival’s stages are dedicated to a particular style like black metal, death metal, doom metal or stoner metal, making possible the presence of groups such as Iron Maiden, Deep Purple, Motörhead, Metallica, Guns N’ Roses, ZZ Top and KISS, as well as that of Slayer, Megadeth, Sepultura, Cannibal Corpse or Anthrax.