Kim Kardashian and Beyonce at a concert.

Kim Kardashian and Beyonce Knowles are becoming fast friends!

At the Watch the Throne concert in Birmingham, England June 22, the E! reality star, 31, and the 16-time Grammy Award winner, 30, stood side-by-side as their respective loves Kanye West, 35, and Jay-Z, 42, performed on stage.

"Kim and Beyonce were dancing all night! They even went into the mosh pit!" a source tells Us Weekly. "It was the most hectic thing ever!"

Kardashian (in a demure black top) and Knowles (in a white tee and leather leggings) did their best to keep a low-profile amidst the sea of fans.

The outing marked the first time the two stars have been photographed in public together. Despite rumors to the contrary, "Kim and Beyonce have always been cool," the source explains. "Beyonce and Jay love Kim and think she's a good match for Kanye."

Kardashian certainly seems so. In a pre-taped interview for Oprah's Next Chapter airing Sunday, she explains how she fell for West after years of friendship. "It's very comforting to have someone who knows everything about you, who respects you, understands you, has gone through similar things," she says. "I feel like I'm at a really happy, good space."

The savvy star and West are on the fast track, an insider recently told Us. "They're seriously talking marriage. And yes, she would [accept his proposal]."