OK! Exclusive: Katharine McPhee Engaged

Sources close to American Idol's have revealed exclusively to OK! that the 23-year-old singer and her actor beau, , 42, are going to get hitched!

"They're definitely engaged," a source on the set of Kat's upcoming film, House Bunny, tells OK!. "They've been talking about it for some time."

For more about Kat and her handsome man, check out the new issue of OK! — on sale now.