Charles Haddon, frontman of electropop trio Ou Est Le Swimming Pool, leapt to his death from a telecommunications mast behind the main stage
at the Pukkelpop festival, police in Belgium said.
The 22-year-old fell to the car park below and was pronounced dead late on Friday night.
The band, based in Camden, north London, had performed at the three-day festival in Hasselt, eastern Belgium, shortly before Haddon climbed up the mast.
Police are treating the death as suicide, district attorney Marc Rubens said.
Festival organisers said Haddon's family had been informed.
In a statement posted on their website, they said: "After performing with his band Ou Est Le Swimming Pool, singer Charles Haddon decided to take his own life.
"Our thoughts and sympathies go out to his family and friends."