The now former couple's reps confirmed the news to People magazine on Monday, saying, "Diane Kruger and Josh Jackson have decided to separate and remain friends."
The often inseparable duo lived together in New York and had homes in both Paris and Vancouver.
Diane and Joshua began dating in 2006 after she split from her husband of five years, French director Guillaume Canet.
Rumors had been circling the couple since last year after reports surfaced that she was spotted making out with "The Walking Dead" star Norman Reedus.
In December, the New York Daily News reported that the actress was "wildly making out" with Norman in an East Village watering hole after showing up at 12th Street Alehouse around 1:30am.
"They were laughing and having fun and then she just literally got out of her chair and straddled him and we were all like, 'what the hell,'" an onlooker told the paper. "They were all over each other. She was a lot more aggressive than him."
Another witness told the Daily News, "they were making out on top of each other, holding hands."
Both denied the story.
In February, the duo put up a united front, as they attended the opening night of Second Stage Theatre's "Smart People," in which Joshua starred in. They posed for photos with their arms around each other.
It was the last time they stepped out together.
Last year, Joshus spoke to People about the secret to his longtime romance.
"I mean it's so banal. It's not always easy because nothing in life that's worth doing is always easy," he added. "I understand at 37 better than I ever did at any other time in my life what the phrase like, 'Love's labor' really means. It's work. But it's work that rewards itself many times over."