Representatives for 'We Can't Stop' singer Miley and Hunger Games actor Liam Hemsworth revealed to People on Monday night (16 September) that the engagement is off.
Reps didn't provide any further details but a source told E! News that Miley initiated the split and Liam spent the weekend moving his belongings out of Miley's home in Los Angeles.
Neither Miley nor Liam has made any comment yet.
The news came amid rumours of a split that were sparked when eagle-eyed Twitter users noted that Miley had stopped following Liam on the social networking website.
Miley and Liam's last public appearance together was 8 August when they attended the Los Angeles premiere of Liam's movie Paranoia together. It was the first time they'd been seen on a red carpet together in over a year.
Former Hannah Montana star Miley and Liam met on the set of romantic drama The Last Song back in 2009. After three years of dating, Liam popped the question with a 3.5-carat diamond ring from Neil Lane on 31 May 2012.
Since then, the couple have faced plenty of speculation over the state of their romance. Rumours of a break-up first swirled earlier this year but in May it was claimed the pair had simply decided not to rush a wedding and were happy just living together for now.
Split rumours surfaced again at the weekend when Miley is said to have stopped following Australian actor Liam on Twitter.
In a twist, news of the break-up came the same week an interview with Miley was published in Harper's Bazaar magazine, where she said she didn't have time to "deal with" a wedding right now.
Miley has been busy promoting new album Bangerz, while Liam is gearing up for publicity duties for the new Hunger Games movie Catching Fire.