The reality star made the trip across the pond to be there for the actor.
London's Royal Festival Hall lit up with Hollywood glamour on Tuesday for the world premiere of Wonka, where 27-year-old Timothée Chalamet took center stage in a vibrant Tom Ford suit and a striking Cartier necklace.
Chalamet posed on the red carpet alongside his co-stars, and graciously interacted with fans and snapped selfies.
While Kylie Jenner didn't make a splash on the red carpet, a source tells ET that the 26-year-old reality TV star and business mogul was in London to support Chalamet during the promotional activities for Wonka.
An eyewitness tells ET that Jenner was spotted at The Corinthia Hotel, just steps away from Chalamet. The makeup mogul made a statement in a strapless, black leather ensemble, showcasing her signature style.
Meanwhile Chalamet, who takes on the role of the titular character in Wonka, was joined by a stellar cast at The Royal Festival Hall, including Sally Hawkins, Rowan Atkinson, Hugh Grant, Olivia Colman, Keegan-Michael Key, and Calah Lane.
In Wonka, Chalamet breathes life into the iconic character previously portrayed by Gene Wilder in 1971's Willy Wonka & the Chocolate Factory and Johnny Depp in 2005's Charlie and the Chocolate Factory. The film promises a fresh perspective on the beloved character's origin, a departure from previous cinematic interpretations.
Chalamet and co-star Hugh Grant sat down with ET's Cassie DiLaura during a press day in London on Wednesday, and the leading man opened up about how "crazy" it feels getting to play the iconic character.
"I grew up on that Gene Wilder film, and I'm hugely admiring of the Tim Burton/Johnny version," Chalamet said. "And this [version] is different. This is the origin [of] Wonka."
"It's not Charlie and the Chocolate Factory," Chalamet explained. "People are suspicious of any new retelling of beloved characters. But I think Paul King, our director, pulled this one off. I'll let people judge for themselves."
"It was a dream come true!" Chalamet shared. "I feel like an honorary Brit, with Hugh Grant and Olivia Coleman and Rowan Atkinson!"
"This is an insane cast and a very unique experience as a young American to walk into this world, this sort of Paddington creative universe that already existed," Chalamet said, referring to the famed 2014 British comedy also directed by King.
This isn’t the first time Jenner has traveled for Chalamet. Earlier this month, the Kardashians star made a stylish arrival to the Saturday Night Live after-party, following her rumored boyfriend, Chalamet's, hosting gig.
The beauty mogul was photographed as she made her way inside the venue in Midtown, New York, in a chic, all-black ensemble. Jenner kept things semi-casual, as she wore an off-the-shoulder shirt, paired with black pants and matching heels. Adding more drama to her evening look, the mother-of-two rocked a pair of dark sunglasses and held onto a tiny purse as she made her way into the party.
Chalamet -- who arrived ahead of Jenner -- kept the vibes casual as he wore a multi-colored hoodie with a purple jacket over dark-washed denim and sneakers.
Jenner and Chalamet's appearance at the SNL after-party came a little over a week after they both attended the same event in New York City. The pair -- who have been rumored to be dating since April -- walked the carpet separately at the WSJ Magazine 2023 Innovator Awards.
Inside the event, the pair were spotted chatting but did not appear to show any PDA.
In September, Jenner and Chalamet stepped out together publicly for the first time at Beyoncé's Renaissance World Tour stop in Los Angeles. The same month, the duo packed on the PDA at the U.S. Open.
A source at the time told ET that Jenner and her new beau are confident in their relationship and that's why she "felt comfortable stepping out with Timothée."
The source said it's "because she is confident and secure in their relationship" that she decided Beyoncé's concert would serve as the first public outing and she "feels like she can be herself with him" and "really likes that."
The source added that the pair "also connect on a deep level."
"Timothée is also a family man and they relate to each other about that," the source said. "Kylie’s friends and family think Timothée is great and love seeing her happy."