Rihanna and Britney Spears S&M performance! Billboard Awards 2011!

Britney Spears joins Rihanna onstage for a performance at the 2011 Billboard Music Awards held at the MGM Grand Garden Arena on Sunday (May 22) in Las Vegas, Nev.

Rihanna, 23, started off the performance of “S&M” before Britney surprised the crowd to perform her verse from their remix version of the song.

Britney, 29, will be hitting the stage later in the show to perform “Till the World Ends” alongside her Femme Fatale tour partner Nicki Minaj.