Kate Hudson & Matthew Bellamy ENGAGED!

Kate Hudson (32) and Muse frontman Matthew Bellamy (32) -- who are expecting their first child together -- are ENGAGED TO BE MARRIED.

Kate made the big announcement today (Wednesday) on the Today Show (where Kate was promoting her latest movie Something Borrowed) after host Matt Lauer's eyes landed on a massive square-cut diamond on her ring finger!

"I haven't really announced it," Kate beamed. "I was waiting for someone to notice."

Kate and Matthew have been together for about a year. And they got engaged around a week ago in NYC. Kate said the proposal was "very romantic."

This will be the second marriage for Kate. Her 6-year marriage to Black Crows singer Chris Robinson ended in 2006 -- and they remain very amicable, which is, of course, awesome because they have a son, Ryder (7), together.

Ooo, and here's a photo of the apparently 9-carat ring! Gorj!

Congrats to Kate and William oops Matthew!

Love!

xo Haley-O

Photo: Fame Pictures | Source