American actress Kristen Stewart, who was romantically involved with Robert Pattinson in both the Twilight movie series and in real life, is for the first time speaking publicly of her current love interest - another woman.

Stewart, 26, spoke with the British edition of Elle magazine in an interview to be published in its September issue which hits newsstands on Aug 3 about her on-again, off-again year-long relationship with visual effects producer Alicia Cargile.

"... I'm just really in love with my girlfriend," she said. "We've broken up a couple of times and gotten back together, and this time I was like, 'Finally, I can feel again.'"

Indeed, she arrived hand-in-hand with Cargile for the premiere of her latest film, Woody Allen's Cafe Society, at the 69th Cannes Film Festival in May this year.

The couple had broken up in October 2015 and Stewart began an affair with a French singer, named Soko, whose full name is Stephanie Sokolinski.

Us Weekly broke the news of Stewart and Soko's split in May.

Earlier, Stewart had dated British actor Pattinson, who played a telepathic vampire named Edward Cullen in the Twilight movies based on a series of books.

Cullen falls in love a human named Bella Swan, played by Stewart, and they have a child together.

Two stars of the same film series falling in love made for big headlines in celebrity magazines and websites. But the story turned scandalous when photos surfaced that showed Stewart was kissing and hugging the director of her film Snow White And The Huntsman, Rupert Sanders, who at 44 was twice her age and married, when she was still seeing Pattinson.

She said her earlier relationships with men was a reason that she has now gone public about her affair with a woman.

"When I was dating a guy, I was hiding everything that I did because everything personal felt like it was immediately trivialised, so I didn't like it," she told Elle UK. "We were turned into these characters and placed into this ridiculous comic book, and I was like, 'That's mine. You're making my relationship something that it's not.' I didn't like that."

Something clicked when she met Cargile, she said.

"It changed when I started dating a girl. I was like, 'Actually, to hide this provides the implication that I'm not down with it or I'm ashamed of it,' so I had to alter how I approached being in public. It opened my life up and I'm so much happier."