Here is everything you need to know about Cyrus' new flame.
WHO IS KAITLYNN CARTER?
With 800,000 Instagram followers, Carter is a social media influencer.
Before meeting her reality TV star ex Brody Jenner, Carter graduated from the University of New Hampshire in 2010 with an English major.
She then started a fashion blog called Hey, Miss Carter, which she hasn't updated since her wedding in July last year.
She also runs a fashion e-commerce website called Foray Collective, which launched in 2015 and profiles emerging designers.
Carter recently founded her own skincare line called selfe, which is yet to launch.
Aside from blogging, Carter is a cast member on the rebooted show The Hills: New Beginnings, alongside Jenner.
The show premiered in June on MTV on Foxtel and has documented the pair's relationship struggles.
In the most recent episode, the couple had a fight because Jenner told a woman he had an "open relationship" with Carter.
On an earlier episode of the show, Jenner's former best friend, reality TV star Spencer Pratt, said he didn't like Carter while also revealing she had hardly any Instagram followers before she started dating Jenner.
Jenner rose to fame on the 2006 reality show The Hills, in which he dated the main star, Lauren Conrad. He has also appeared on episodes of Keeping Up With The Kardashians as the half-brother of Kendall and Kylie Jenner.
HOW DOES SHE KNOW MILEY CYRUS?
Given the two are on opposite ends of the fame spectrum, it is curious how they came to meet in the first place.
Cyrus, whose net worth is a staggering $US160 million ($NZ247 million), shot to global superstardom starring in the hugely-successful Disney Channel show Hannah Montana, which first aired in 2006.
US media reports Carter met her recently through Cyrus' older sister, Brandi, 32.
Carter visited Brandi at her home in Nashville last month to guest host an episode of Brandi's podcast, Your Favourite Things.
Carter and Cyrus took to their Instagram pages to post individual photos on giant inflatables in Brandi's pool, while Brandi announced the reality star would be co-hosting with her on her podcast.
Carter was then among Cyrus' entourage at Sunny Hill Festival in Kosovo, where she performed in early August.
Cyrus and Carter also both live in Malibu, so there is a chance they have met before, however this union appears to be fairly recent.
WHAT IS HER HISTORY WITH BRODY JENNER?
Carter met Jenner, the stepbrother of Kim, Khloe and Kourtney Kardashian, at a party in Los Angeles in 2013.
They didn't make their relationship public until May 2014.
In a joint interview last year, Jenner revealed he chased Carter, who said she realised fairly quickly he was the one.
"He was really honest about what he wanted, no messing around, and I found that really charming and refreshing. Pretty soon after we started dating, I thought it could be for life," Carter told People.
Jenner had a falling out with Kim Kardashian over Carter because she wasn't invited to her wedding to rapper Kanye West in May 2014. Jenner was invited however was denied a plus one, so he boycotted the wedding.
In 2016, Jenner proposed to Carter in Bali, Indonesia, where they would end up getting married in June 2018.
They appeared in the first episode of The Hills: New Beginnings two months ago, where Jenner called her a "psychopath" after she yelled at him for getting home late after a party.
The show began filming late last year.
The pair announced their split just over a week ago.
Cyrus and Hemsworth married in December 2018 after dating on-and-off for 10 years.
"Liam and Miley have agreed to separate at this time," a rep for Cyrus confirmed to E! and People in a statement.
"Ever-evolving, changing as partners and individuals, they have decided this is what's best while they both focus on themselves and careers."
Cyrus and Hemsworth met while filming the movie The Last Song in 2009.
They were previously engaged in June 2012 but called time on the relationship the following year.
In 2016, they announced the engagement was back on, and their surprise nuptials last year took place at their home in Tennessee.
