Katy Perry, Justin Timberlake Waking Up In Vegas For iHeartRadio Music Festival

Miley Cyrus, Bruno Mars and more will also make the trek to Sin City for the September fest.

What happens in Vegas usually stays in Vegas, unless it's the star-studded iHeartRadio Music Festival, taking place this year on September 20 and 21 at Las Vegas' MGM Grand Arena. On Monday (July 15), Ryan Seacrest announced the A-list lineup for the third annual Sin City party.

Friday's show will be headlined by acts from all genres, including Katy Perry, Queen, Adam Lambert, Fun., Elton John, Keith Urban, J. Cole, Muse, Tiesto and Chris Brown. The next day, Justin Timberlake, Tim McGraw, Bruno Mars, Phoenix, Maroon 5, Zedd, Ke$ha, Miguel, Thirty Seconds to Mars and Benny Benassi will all take the stage.

In addition to the main show action on day two, this year's festival will host an additional batch of performances held at The Village, taking place on September 21 at The Lot. Performers for the additional stage include Miley Cyrus, The Wanted, Jason Derulo, Ne-Yo, The Band Perry, Avril Lavigne, Krewella, Cher Lloyd, Twenty One Pilots, Pete Tong and AWOLNATION.

Other guests are expected to be announced closer to the show dates. Tickets will go on sale on Saturday.

The fact that both Miley and Katy are playing the festival might mean fans will finally get to hear some new music from the two pop divas. Katy has been hard at work on her next album, the [article id="1709867"]follow-up to Teenage Dream[/article]. And, Miley is slated to drop new music by year's end. Whereas Katy's project has been kept under wraps, Miley dropped her single, [article id="1708342"]"We Can't Stop,"[/article] last month.