Is Hilary Duff having a boy or a girl ?

Is it a boy or a girl for Hilary Duff and husband Mike Comrie?

The pregnant 24-year-old revealed she and her hockey player hubby are expecting a baby boy -- letting it slip on today's episode of "The Ellen DeGeneres Show."

The former Disney star had Ellen try and guess the baby's sex -- and when she said "boy," Duff confirmed the news.

"it’s kind of like a little alien has taken over your body," Duff says of the pregnancy. "You just don’t quite feel normal.  But it’s cool.It’s been good."