The 28-year-old singer excitedly announced her engagement on her Instagram page on Monday, tweeting a picture of a gi-NORMOUS heart-shaped rock on her wedding finger.
The Born This Way star captioned it: ‘He gave me his heart on Valentine’s Day, and I said YES!’
Gaga and the Zero Dark Thirty actor have been dating on and off since 2011. They met whilst recording her video for You And I – a song about an ex-boyfriend of hers.
US reports say they celebrated in New York restaurant Joanne’s Trattoria, owned by Gaga’s family.
The couple have been inundated with messages from their fans congratulating them on the news, with the hashtag #CongratsGagaAndTaylor trending moments after their happy news broke.
Speaking of Kinney to Ellen DeGeneres in November 2013, Lady Gaga said: ‘He’s a hidden weirdo. He is extremely strange, actually, and we complement each others’ weirdness.
‘That’s actually one of the first things he ever said to me. It’s a Dr. Seuss quote, that you find in someone else a “compatible weirdness”. And it was one of the first things he said to me.’