Kruger, 40, and Jackson, 38, hadn’t been spotted on a red carpet together since February, where they attended the opening of Jackson’s Broadway play, and some fans started speculating that the pair had split when Jackson wasn't there to celebrate her 40th birthday with her on July 15.
The German actress posted this Instagram, captioned: "It's my party and I will cry if I want to #happyFridayeverybodyandthankyouforallthebirthdaywishes #anewbeginning."
Though the couple were together for over a decade, they never married, and Jackson previously explained that the reason they hadn’t tied the knot came down to religion.
"I can tell you why we're not married: We're not religious," he told E Online in 2014. "I don't feel any more or less committed to Diane for not having stood in front of a priest and had a giant party. We're both children of divorce, so it's hard for me to take marriage at face value as the thing that shows you've grown up and are committed to another person."
The couple, who lived together in New York, began dating after Kruger split from her husband of five years, French director Guillaume Canet.