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Performers for 2013's iHeart Radio Music Festival / Justin Timberlake
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Performers for 2013's iHeart Radio Music Festival / Ke$ha
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Performers for 2013's iHeart Radio Music Festival / Katy Perry
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Performers for 2013's iHeart Radio Music Festival / Zedd
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Performers for 2013's iHeart Radio Music Festival / J. Cole
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Performers for 2013's iHeart Radio Music Festival / Bruno Mars
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Performers for 2013's iHeart Radio Music Festival / Adam Lambert
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iHeart Radio unveiled the line-up on Monday for its third annual music festival in Las Vegas. Among the headliners are Justin Timberlake, Elton John and Bruno Mars. The more surprising news was that Katy Perry will return to the stage that weekend and Queen will also team up with singer Adam Lambert.

The iHeart Radio Music Festival will take place in Vegas on September 20 and 21 in the MGM Grand Arena, Billboard reports. Seeing Timberlake as one of the show's headliners came as no surprise really. He made a triumphant comeback this year with The 20/20 Experience, 2013's best-selling album so far. His performance for iHeart Radio will happen just before the release of The 20/20 Experience - Part 2 of 2.

Perry has been hard at work on a follow-up to 2010's mega-successful Teenage Dream album. With Katy's name among this year's performers, it is safe to say that she will probably premiere new material from her highly-anticipated third studio album. Katycats, be ready!

Lambert recently announced his departure from RCA records. The "American Idol" alum has seemed to move on quickly with new projects in the works. He will join the cast of "Glee" and will also team up with Queen during the band's iHeart Radio performance. This could be a sign of new music to come from Queen with Lambert.

This year's iHeart Radio Music Festival is eclectic with the rest of the line-up. Country singer Keith Urban will perform along with pop acts Chris Brown and Maroon 5. Rapper J. Cole is also listed with the likes of EDM DJs Zedd and Tiësto. Rock will be represented with performances by Phoenix and Thirty Seconds to Mars. People from many genres will be coming together that weekend in Las Vegas.

iHeart Radio Music Festival Performers

Justin Timberlake
Katy Perry
Elton John
Muse
Tiësto
Chris Brown
Keith Urban
J. Cole
fun.
Bruno Mars
Phoenix
Zedd
Maroon 5
Miguel
Tim McGraw
Ke$ha
Thirty Seconds to Mars
Benny Benassi
Special live appearance by Queen and Adam Lambert
Other special surprise guests

iHeartRadio Music Festival Village (multiple stages)

Miley Cyrus
Avril Lavigne
AWOLNATION
Pete Tong
Twenty One Pilots
Jason Derulo