Rihanna is definitely sexy enough to walk the runway at the Victoria's Secret Fashion Show, but instead, she hit the catwalk to perform her hit song "Diamonds."

Wearing exposed stockings and killer heels, RiRi sexed up the stage ... even touching some of the supermodels as they strutted by in their lingerie. After the show, the songstress struck a candid pose backstage with a few of the VS beauties.

Also in the audience ... teen sensation Justin Bieber. Lucky guy!