The two co-star in the upcoming drama Equals.
"She's so talented," Hoult told me at South by Southwest, where he helped unveil the new Jaguar XE at Boffin's Lab Powered by Jaguar and Wired Insider event. "I really can't speak highly enough about her. She's a talented, lovely and a wonderful girl…She's just got such a smart approach to her work and she's a real artist."
In the film, Hoult and Stewart live in a futuristic world where all human emotion has been eradicated.
"My character starts to get what they consider a sickness, where he starts to have nightmares and feel things and he's like, 'Hang on! What's going on here?'" Hoult said. "And then he notices Kristen's character and they start to develop this relationship in a world where people aren't allowed to have relationships, where they don't exist. It's basically a love story."
Hoult also has not one, but two movies coming up with Charlize Theron.
After the they shot Mad Max: Fury Road, the Oscar winner asked that Hoult join the cast for the thriller Dark Places.
"She's a brilliant lady to watch work and be around," Hoult said of Theron. "And she also has a good sense of humor, so she takes my s--t and gives it back to me.
"There's a balancing act where you're there to work, but you know what? You'll take the piss out of me and I'll take the piss out of you," Hoult said. "You've got to lighten the mood sometimes."
For more from SXSW, check out E! News tonight at 7 p.m. and 11 p.m.