Rihanna Dating Rob Kardashian!

Rihanna Dating Rob Kardashian!

Rihanna is keeping up with one very handsome Kardashian.

The "S&M" singer, 24, shared an action-packed day with E! reality star Rob Kardashian, 25, on August 25, multiple insiders tell the new issue of Us Weekly (out now). After go-karting at Racer's Edge Indoor Karting in Burbank, California, the pair partied at L.A.'s Playhouse nightclub later that evening.

"They were sitting closely at the club, whispering in each other's ears and clearly flirting," an eyewitness says. A Kardashian source adds that "Rihanna and Rob have been flirting for a while."

Until recently, Kardashian was linked to a Rihanna competitor -- British singer Rita Ora, 21. Rihanna was so taken with Kardashian at Playhouse, she didn't even visiting a neighboring VIP: her ex, Chris Brown, 23!

For more details on the stars' surprise courtship -- and how Rihanna avoided contact with Brown during her night on the town with Kardashian -- watch this week's Hot Stuff Video, as explained by Us Weekly Senior Editor Ian Drew and special guest, nightlife icon Amanda Lepore.

Also in the roundup: Kate Hudson thinks Lea Michele is a diva on the Glee set, Taylor Armstrong packs on the PDA with boyfriend John Bluher, and much more!