Martin Garrix delivered one of the biggest surprises of Tomorrowland Belgium by premiering his long-awaited collaboration with U2, titled “Fireflies,” during his headline performance on the festival’s Mainstage.

The Dutch DJ and producer unveiled the unreleased track before bringing out U2 guitarist The Edge, who joined him on stage to perform the song live in front of thousands of festivalgoers in Boom, Belgium. The unexpected appearance drew one of the loudest reactions of the night as fans witnessed the first-ever live performance of the collaboration.

“Fireflies” marks another high-profile crossover for Garrix, blending his melodic electronic production with U2’s signature arena-rock sound. The track features vocals from Bono, while The Edge’s unmistakable guitar work adds a soaring rock element to the festival anthem. Although Bono was not present at Tomorrowland, The Edge’s appearance gave fans a preview of what is shaping up to be one of Garrix’s biggest releases of the year.

The collaboration had been the subject of speculation for months after Garrix hinted at working with U2. Fans attending Tomorrowland were treated to the full debut, with videos of the performance quickly spreading across social media as viewers praised both the song and the surprise guest appearance. Online reactions described the performance as one of the standout moments of the festival’s opening weekend.

According to reports following the performance, “Fireflies” is scheduled for digital release on July 24, giving fans less than a week to wait before the studio version becomes available on streaming platforms.

Garrix’s Tomorrowland set featured many of his biggest hits alongside new material, but the debut of “Fireflies” became the defining moment of the performance. The surprise reinforced Tomorrowland’s reputation for exclusive premieres and special guest appearances while adding another major collaboration to Garrix’s growing catalog.