The Coldplay frontman was spotted pashing blonde beauty Kate Bosworth at a party, according to Star magazine.
"I couldn't believe my eyes," an eyewitness told the mag. "There was Chris totally making out with Kate in front of other people. At first I thought it might be Gwyneth, but when she came up for air, it was clear the woman was Kate!"
That's a pretty big claim one that could totally screw up their marriage. And since it came from Star magazine we're going to take it with a pretty big grain of salt.
Chris's rep was quick to deny the rumour: "This story is entirely untrue. [Kate] may have been in the same room with [Chris], but he is not having an affair, was not kissing her or holding her hand."