Kate Walsh's New Boyfriend Revealed

05/04/2007 at 08:00 AM EDT

Grey's Anatomy star Kate Walsh has been coy about the new man in her life, recently telling PEOPLE he's "a great guy, but I'm not giving you a name."

But now, PEOPLE reports in this week's issue, the mystery has been solved. Walsh, 39, is dating Alex Young, a production co-president at 20th Century Fox, with a string of blockbuster credits including X-Men: The Last Stand and Fantastic Four.

"He's a hotshot," says a friend. "But Alex also has substance. He's a good guy." (Walsh's rep declined to comment.)

Walsh, who stepped out with Young at an April 28 fund-raiser for Barack Obama in Los Angeles, has become pretty hot herself. On Thursday night, she starred in a two-hour special episode of Grey's, which featured her character, Dr. Addison Montgomery-Shepherd, contemplating a move to another hospital.

The storyline is the basis for a possible spinoff starring Walsh and Taye Diggs.

And Walsh recently told Best Life magazine she's a late-bloomer in love, but is finally ready for a serious relationship. "I don't need someone with a hot body," she said. "He can be fat or overweight and have a belly. It's very much about style and substance and humor, interest, curiosity and really being smart."