The Almost Famous star began dating the British singer last year (10) and the pair is expecting a baby together.
Bellamy proposed to Hudson last week (end24Apr11) in New York, but the actress kept the engagement secret until she was quizzed about a diamond ring on her wedding finger.
Appearing on America's Today Show on Wednesday (27Apr11), host Matt Lauer picked up on the new jewellery item before Hudson confirmed, "I haven't really announced it, I was waiting for someone to notice."
Hudson admits that despite their pending parenthood, they are in no rush to book a date for the nuptials.
She says, "I don't (have a date yet). Matt Bellamy, he's a beautiful man. I'm excited. But I think we're just going to sort of sit and do the baby thing for a little bit."
Hudson revealed the couple doesn't yet know the gender of the baby, although she's confident it's a girl - and the new tot is already taking after her mum, Hollywood star Goldie Hawn.
The actress adds, "She's so nuts in here. She's so wild. I kind of feel like it's got the (Goldie) Hawn gene. It's got my mom's lineage for sure. It's like dancing every day."
Hudson has been married once before - to Black Crowes rocker Chris Robinson, who is father to her seven-year-old son, Ryder.