Getty Images for Clara Lionel Foundation

On Thursday night a slew of stars braved the rain and headed to the First Annual Diamond Ball at The Vineyard in Beverly Hills, and this was a charity gala for Rihanna's Clara Lionel Foundation. RiRi founded the organization in 2012, which "works to improve the quality of life for communities globally in the areas of health, education, arts, and culture."

Rihanna wowed in a rosy-hued Zac Posen dress and Chopard jewels while Kim sexed it up in an Alexander Wang for Balenciaga ensemble. After posing on the red carpet and inside the party, Rihanna changed into a strapless black gown and hit the stage. She was introduced by none other than Brad Pitt (more on that later), and she performed a medley of her biggest hits, including "Diamonds," "Pour It Up," "Umbrella," and "Run This Town" with a full orchestra.

The singer tweeted:
    "Feel so lucky to have an evening like this, to spend with people with hearts like mine, who want to change and save lives at any cost! There’s so much to do, and I can’t do it all by myself, so I have to thank all of the supporters of and people who donated to #TheClaraLionelFoundation Looking forward to seeing you later this evening."

Kris Jenner was there as well, and while she showed some cleavage, she didn't quite give daughter Kim a run for her money: