Cyrus and boyfriend of three years Liam Hemsworth announced their engagement on Wednesday (June 6).
The former Hannah Montana star posted a message via her Twitter account, thanking fans for their support and saying: "I feel like all my dreams are coming true."
She was later photographed in Beverly Hills wearing a large diamond engagement ring crafted by jeweller Neil Lane, who said Hemsworth "wanted something really romantic and beautiful".
Expert jewellery appraiser Kenneth Lejman told the New York Daily News: "Assuming it's reasonably high quality, I would estimate it at $250,000."
There is no word yet on when Cyrus and Hemsworth plan to hold their wedding.