Britney Spears definitely has a celeb fan in Nicole Richie!

The reality TV star-turned mother/designer just shared the above video with her fans, showing her having a dance off with a friend to Britney's 2001 hit "I'm a Slave 4 U."

Richie, who nails the singer's choreography, added that she "can't wait to dance tonight" -- suggesting she'll be attending Brit's L.A. show at the Staples Center.

Check out Nicole's killer routine -- and re-watch Britney's sexy video below.