Iggy Azalea & Sam Smith Lead 2015 iHeartRadio Music Awards Nominations

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Iggy Azalea performs on stage at Park City Live during the 2015 Sundance Film Festival at Park City Live! on January 24, 2015 in Park City, Utah.

With five nominations each, Iggy Azalea and Sam Smith are the early leaders heading into the 2015 iHeartRadio Music Awards, nominations for which were announced Wednesday. Taylor Swift and Ariana Grande are close behind with four nods each.

On the night, Iggy, Sam, Taylor, Ariana and Luke Bryan will face off for the top honor, artist of the year.

This year's March 29 ceremony returns to L.A.'s Shrine Auditorium, and will be broadcast live on NBC and aired simultaneously on iHeartMedia stations and across the network's digital music platform.

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The second-annual gala celebrates the year's top artists and music played across iHeartMedia's network. Trophies will be handed out for song of the year, best collaboration, best new artist, country song of the year, hip hop/R&B song of the year, dance song of the year and alternative rock song of the year, while fans will get a chance to determine the categories for best fan army, best lyrics and the inaugural "Renegade Award." The latter category recognizes "an emerging standout artist that defies convention and breaks boundaries" and is sponsored by Jeep.

Performers for this year's show will be unveiled in due course.

The inaugural 2014 iHeartRadio Music Awards telecast was watched by more than 5.5 million people, organizers say, and the telecast generated a staggering 8.5 billion social impressions. Fans cast more than 65 million votes using hashtags on Facebook and Twitter.

Rihanna was the big winner at the 2014 event, taking out artist of the year, song of the year, hip hop/R&B song of the year and best fan army. Other winners included Lorde (best new artist), Blake Shelton (country song of the year) and Avicii (EDM song of the year) while the performers on the night included Luke Bryan, Bastille, Ariana Grande, Blake Shelton, Thirty Seconds to Mars and Kendrick Lamar.

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The 2015 iHeartRadio Music Awards will be executive produced by John Sykes, Tom Poleman and Liz Kelly of iHeartMedia, along with Ian Stewart and Hamish Hamilton of Done and Dusted Inc., who will also produce the show for NBC Studios. Hamilton will also direct.

Nominations for the 2015 iHeartRadio Music Awards are:

Artist of the Year:
Ariana Grande
Iggy Azalea
Luke Bryan
Sam Smith
Taylor Swift

Song of the Year:
"All About That  Bass" - Meghan Trainor
"All of Me" - John Legend
"Happy" - Pharrell Williams
"Shake It Off" - Taylor Swift
 "Stay With Me" - Sam Smith

Best Collaboration:
"Bang Bang" - Jessie J + Ariana Grande + Nicki Minaj
"Dark Horse" - Katy Perry featuring Juicy J
"Fancy" - Iggy Azalea featuring Charli XCX
"Problem" - Ariana Grande featuring Iggy Azalea
"Talk Dirty" - Jason Derulo featuring 2 Chainz

Best New Artist:
Cole Swindell
Iggy Azalea
Meghan Trainor
Sam Smith

Country Song of the Year:
"Bartender" - Lady Antebellum
"Burnin' It Down" - Jason Aldean
"Dirt" - Florida Georgia Line
"Give Me Back My Hometown" - Eric Church
"Play It Again" - Luke Bryan

Hip Hop/R&B Song of the Year:
"Don't Tell 'Em" - Jeremih featuring YG
"Drunk in Love" - Beyoncé featuring Jay Z
"Flawless" - Beyoncé
"Loyal" - Chris Brown featuring Lil Wayne and Tyga
"New Flame" - Chris Brown featuring Usher and Rick Ross

Dance Song of the Year:
"Animals" - Martin Garrix
"Blame" - Calvin Harris featuring John Newman
"La La La" - Naughty Boy featuring Sam Smith
"Summer" - Calvin Harris
"Waves" - Mr. Probz 

Alternative Rock Song of the Year:
"Come With Me Now" - KONGOS
"Do I Wanna Know?" - Arctic Monkeys
"Fever" - The Black Keys
"Something From Nothing" - Foo Fighters
"Take Me to Church" - Hozier 

Best Lyrics:
"All of Me" - John Legend
"Blank Space" - Taylor Swift
"Counting Stars" - OneRepublic
"Habits (Stay High)" - Tove Lo
"Stay With Me" - Sam Smith
"Thinking Out Loud" - Ed Sheeran 

Best Fan Army:
5SOSFAM - 5 Seconds of Summer
Arianators - Ariana Grande
Bey Hive - Beyoncé
Team Breezy - Chris Brown  
Sheerios - Ed Sheeran
Church Choir - Eric Church
Directioners - One Direction
Selenators - Selena Gomez
Mendes Army - Shawn Mendes
Swifties - Taylor Swift

Brantley Gilbert
Charli XCX
Iggy Azalea
Meghan Trainor