The line-up for Clear Channel's iHeartRadio Music Festival 2012 was unveiled this morning via special live announcement by Ryan Seacrest—and it looks to be another once in a lifetime event.

Among those appearing will be Taylor Swift, Rihanna, Usher, Linkin Park, the recently reunited No Doubt, Brad Paisley, Green Day and more than a dozen other A-list performers.

The two-day festival, slated for Sept.21-22 at the MGM Grand in Las Vegas and billed as "the Biggest Live Music Event in Radio History," will be streamed live by Yahoo!, Clear Channel's web and mobile webcast partner for the event.

This year's iHeartRadio Music Festival follows last year's inaugural event--tickets for which sold out 10 minutes after being made available to the public—and likewise has focused on superstar talent.

This year's officially announced lineup includes Taylor Swift, Aerosmith, Rihanna, Usher, Bon Jovi, Lil Wayne, Green Day, Swedish House Mafia, No Doubt, Brad Paisley, Pitbull, Deadmau5, Miranda Lambert, Enrique Iglesias, Linkin Park, Jason Aldean, Pink, Mary J. Blige, Calvin Harris & Shakira.

Kinda boring...still gonna try to win tix though

Yeah, I don't really care about any of those people.

I would die to see those 2 bands in 1 concert

I wonder if Usher is going to perform though after what happened?

Since Enrique is going to be there do ya'll think they'll add Jen to the lineup??