Cyrus has more than 5.2 million followers on Twitter, and they were looking at more than her nail polish when she sent out a recent tweet about her manicure. In the message, Cyrus confessed to being "obsessed with @jennahipp nail foundations!" but she didn't mention the giant rock on her ring finger.
Speculation is that the diamond is at least three carats.
She was spotted wearing the same sparkler on her ring finger at a charity event over the weekend.
But in Hollywood, just because someone's wearing what looks like an engagement ring, that doesn't guarantee wedding bells.
Singer and actress Selena Gomez recently sported what looked like an engagement ring, but reports say her boyfriend, pop star Justin Bieber, had given her a pre-engagement ring.
So far there's no word on when - or if - there's a wedding in the works for Cyrus, 19, and Hemsworth, 22.
Cyrus and Hemsworth reportedly already share a dog.