American rock band Foo Fighters finally revealed the mystery pop star who collaborated with them on their upcoming album — Justin Timberlake.

Frontman Dave Grohl has been teasing the identity of a "big star" who lent his vocals in one of their songs from their upcoming ninth LP, "Concrete and Gold."

Grohl told Rolling Stone how the collaboration was conceived.

"We'd drink whiskey in the parking lot. He was really, really cool. Then the night before his last day, he says, 'Can I sing on your record? I don't want to push it, but – I just want to be able to tell my friends,'" he said.

Grohl added that Timberlake's contribution was a simple "la la la" but that Timberlake "nailed" the part.

The identity of the "mysterious collaborator" was first floated in June when Grohl talked to BBC Radio 1. He said that the collaborator "is probably the biggest pop star in the world" and that he will be featured in one of the heaviest songs on the record.

Timberlake will not be the only star who collaborated with the Foo Fighters for "Concrete and Gold."

The Beatles' Paul McCartney played drums on one of the tracks. Grohl called McCartney "the most wonderful guy in the world" and that McCartney agreed to help even if he haven't heard the track yet.

Other collaborators are the Bird and the Bee's Inara Geroge, the Kills' Alison Mosshart and Boyz II Men's Shawn Stockman.

Foo Fighters was formed in 1994 when the band Nirvana dissolved after the death of Kurt Cobain.

Since then the band has received numerous awards. They have been nominated for the Grammy awards for 27 times, winning 11.

At the 54th Grammy Awards, Foo Fighters was tied with Adele and Bruno Mars for the second most nominations with six and went home as the second big winner with five awards.

"Concrete and Gold" will be released on Sept. 15.