Wearing black bodice and knee-high boots, the blonde singer writhed around on stage as she joined Rihanna to perform hit song S&M.
The scantily-clad pair, who also carried chains, then took part in a pillow fight with their backing dancers at the end of their risqué routine.
Spears, 29, rose up to the stage on a ladder as she joined Rihanna halfway through her performance of S&M.
The audience screamed with delight as she removed her mask and strutted around the stage with the flame-haired songstress.
The pair then faced one another as they slid provocatively up and down poles, much to the crowd’s delight.
Spears later joined hip-hop star Nicki Minaj on stage to perform a segment from her new song Til The World Ends.
Although Spears gave what was probably the most talked about performance at the Billboard Music Awards, the night really belonged to Justin Bieber and Eminem.
The pop star and rapper each took home an incredible six awards from the ceremony, which was held at the MGM Grand in Las Vegas, Nevada.