Selena Gomez attended Sunday night's Billboard Music Awards in Las Vegas in a sexy side cut-out dress in support of her boyfriend Justin Bieber, who took home eight trophies.

The stars wore a variety of ensembles at the music event.  Rihanna embraced the plunging neckline trend in a white pant suit, while Nicki Minaj wore a signature pink wig with a skintight blue bodysuit.

Several stars opted for the traditional black dress, including Selena, Beyonce, Nicole Kidman and Fergie.  Check out the celebrities below, and tell us who looked the best and worst!

CHECK OUT ALL THE WINNERS HERE!

Beyonce

Ke$ha

Joe Jonas

Taylor Swift

Nicki Minaj

Justin Bieber

Fergie

Bret Michaels

Hillary Scott

Kelly Rowland

Travis Barker

Kylie Minogue

Keri Hilson

Trey Songz

Mary J. Blige

Ne-Yo

Nicole Kidman

Rihanna

Snoop Dogg

Bono & The Edge