The 22-year-old 'Hunger Games' star proposed the 19-year-old singer-actress with a 3.5-carat diamond ring last Thursday, reported a magazine.
"I'm so happy to be engaged and look forward to a life of happiness with Liam," Cyrus said.
Cyrus, who shot to fame with the show 'Hannah Montana', has been dating Aussie star Hemsworth for three years. They met in 2009 on the set of their film 'The Last Song', in which they co-starred, and split briefly in 2010 before reconciling a month later.
Cyrus is in the studio working on a new album, while Hemsworth is currently filming 'Empire State' in New Orleans. He will also start filming 'Paranoia' with Harrison Ford and Gary Oldman before beginning production on the second 'Hunger Games' installment.