The young couple, who have been together for around three years, shared their happy news Wednesday.
"I'm so happy to be engaged and look forward to a life of happiness with Liam," Cyrus told People, which first reported the May 31 engagement.
Hemsworth, 22, played Gale in the blockbuster film "The Hunger Games"and is younger brother to Thor himself, Chris Hemsworth. He met Miley, 19, on the set of the 2009 flick "The Last Song."
"Thank you for all the love today :) I'm happy to share this news with you all. I feel like all my dreams are coming true," Cyrus tweeted Wednesday.
The former Hannah Montana, daughter of country singer Billy Ray Cyrus, is now rocking a 3.5-carat diamond set in gold, designed by Neil Lane in collaboration with Liam (check it out here).
"It’s a contemporary design based on vintage aesthetics,” Lane told People. "The light flashes and sparkles no matter where Miley moves her hand."
While Miley is thrilled with her current flasher, just a few months ago she pooh-poohed the notion. In March, Cyrus tweeted about her manicure while rocking a Cracker Jack-style ring on her engagement-ring finger, setting off a storm of speculation.
"I'm not engaged," she said at the time, "I've worn this same ring on this finger since November! People just wanna find something to tal [sic] about! It's a topaz people!"
Not anymore. Congratulations to the young couple.
Follow Matt Donnelly on Twitter @mattdonnelly.