Stephen Colbert has announced his first guest to appear on the debut night of "The Late Show with Stephen Colbert," and he is huge! George Clooney is set to appear on Colbert's new show, which airs for the first time on Sept. 8, according to Time.

"George Clooney will be my first-ever #LSSC guest on September 8th!" Colbert says on Twitter. "Could one of you let him know?"

Colbert is stepping in as the CBS late night show's new host after David Letterman's retirement on May 20. The former host of Comedy Central's "The Colbert Report" got his start as a long-time correspondent for the network's other hit program, "The Daily Show with Jon Stewart," according to TheWarp. Colbert made the announcement the morning after an appearance on Stewart's last day hosting "The Daily Show."

Snagging one of the most famous movie stars on the planet is a huge get for Colbert, who for the first time is shedding his "Colbert Report" character and is hosting "The Late Show" as himself. As Sept. 8 draws nearer, Colbert has been releasing the first set of promos for his new hosting gig. Check out a hilarious one with former Republican Presidential nominee Mitt Romney below!