The 30-year-old star - who shot to fame after winning American Idol in 2002 - shared her joy with her fans on Twitter, writing: "I'm engaged!!!! I wanted y'all to know!! Happiest night of my life last! I am so lucky and am with the greatest man ever."

Kelly recently expressed her hopes that the couple would tie the knot even though they weren't yet engaged.

Last month, she said: "We are totally going to get married. We love each other. We are totally going to get married one day.

"I mean, he's got to put a ring on at some point. But I'll wait it out."

Asked if she has thought about the kind of wedding she wants to have, the 'Stronger' singer said: "Honestly I've never been the girl to plan a wedding. We will totally, probably elope."

Kelly previously called their relationship her "best accomplishment" after years of being unlucky in love.

She said: "I completely fell in love. I did! Welcome to Cheeseville! I don't know. Your priorities kind of shift and you become happier and all that stuff. It's probably my best accomplishment because I think, for me, especially, I just didn't think it would happen."