"Susan Boyle would be perfect," Cowell told Extra, adding that the YouTube singing sensation's version of "Dreamed a Dream" would be the perfect wedding song.
The former American Idol judge also added that Prince William and Prince Harry are fans of Cowell's British X-Factor.
"I'm actually friends with Prince Harry. Well, I wouldn't say friends, per se, but he's come down to the show," Cowell said. "He and I get along very well. He's a very, very nice guy. I like him a lot."
Prince William and Kate Middleton, who got engaged last month after a long courtship, are set to exchange vows at Westminster Abbey on April 29, 2011.
Do you think Boyle should perform at the royal wedding?