The singer posted a picture of her left hand on her Twitter page, ostensibly to promote a brand of nail polish.
“I am sooo obsessed with @jennahipp nail foundations!” Cyrus wrote Thursday.
However, what drew most attention was the sparkler she proudly showed off on her ring finger.
Cyrus was also seen wearing the ring when she and Hemsworth attended Muhammad Ali’s Celebrity Fight Night XIII event in Phoenix, Arizona, on Saturday night.
In addition, a source told OK! magazine that the have actually gotten seriuous about tying the knot.
“They’re still keeping it a big secret, but they’re seriously talking marriage. Liam is crazy about her! Miley wants the whole nine yards as far as a big wedding goes,” the source said.
Hemsworth, 22, and Cyrus, 19, have had an on-off relationship since meeting on the set of the 2009 film “The Last Song.”
Earlier this week, Us magazine cited a source saying that Miley’s wild ways sometimes worry her boyfriend.
“She gets pretty crazy,” a source told the mag. “She’s always out in skimpy outfits and writhing on (Liam). Sometimes he looks embarrassed of her.”