According to Los Angeles court records obtained by RadarOnline.com, the Hunger Games actor filed a petition on Wednesday, August 21, citing "irreconcilable differences."
The 29-year-old listed the marriage date as December 23, 2018, but said the separation date was TBD.
He claimed the estranged couple signed a prenup before their Nashville ceremony.
"Pursuant to the parties' Premarital Agreement, all assets and obligations of each party are his/her separate property," the documents state.
The papers indicate that high-powered divorce lawyer Laura Wasser has signed on to represent him in the court proceedings.
A source told Radar Hemsworth hopes to make a clean, fast break from his partner of nearly a decade.
"He wants to put all of this behind him, move on, and find a fresh start," the source close to the hunk exclusively told Radar.
Hemsworth and Cyrus, 26, announced their separation on August 10 after less than eight months of marriage.
A source close to the actor told Radar he was absolutely “heartbroken” after seeing Cyrus move on with The Hills star Carter, 30, so quickly.
Another source noted that while the "Malibu" singer loves her hubby, she was "bored" in their relationship, and needed more excitement.
A source told Radar that Tish, 52, is confused by how fast the two ladies are moving, and doesn't know what to think about the seemingly fame-hungry Carter.
After her split from Hemsworth, Cyrus released an emotional song about their downfall, titled "Slide Away," in which she speaks about wanting to grow up and let go of her past.
It also includes a cryptic line about "whiskey and pills" which seems to reference rumors of Hemsworth's excessive partying.
As Cyrus focuses on her music and her new girlfriend, Hemsworth attempts to heal. The hunk was recently caught looking somber while bar-hopping with friends in his native Australia.