"The worst kept secret in Hollywood is out. Mario and Khloe are our hosts," Cowell said in a statement to UsMagazine.com Tuesday. "They will debut on our first live show in November and I couldn't be happier."
"I'm so thrilled to become a part of the 'X Factor' family," Kardashian said. "I've been a big fan of the show and look forward to working with Simon and all of the judges. It's going to be so much fun!"
"I'm very excited to be joining the 'X Factor' team. I love the show, and I've been a big fan of Simon Cowell and the judges for a long time. Khloe and I have been friends for years and I know we'll be a great team and have a blast," Lopez said.