Us Weekly is reporting that Charlize was the one who pulled the plug.
The high-profile pair first got together in December 2013, though they had been friends for decades. Us says the duo "decided that their romance was over following their most recent jaunt to the Cannes Film Festival in the south of France."
A year into their relationship, the couple got engaged during a trip to Paris, although neither of them wore rings.
Two had been fairly vocal about their affection toward one another. During an interview in January, "Extra"'s Jerry Penacoli told Sean he seems as happy as he's ever been, to which the "Mystic River" star said, "I can't imagine why," as his girlfriend stood nearby.
In an interview with Esquire UK, Sean said he was ready to be a husband again.
He even said he would consider it his "first marriage," although he's already been married twice before.
"I've had relationships that were not with famous people, or people aspiring to be famous," he said. "And in some cases they went more poorly! But as it turned out, yes, the two marriages I had were with high-profile people, in their own ways. But my romantic life has not been exclusive to that."
He went on to say, "You say I've been married twice before, but I've been married under circumstances where I was less informed than I am today. So I wouldn't even consider it a third marriage, I'd consider it a first marriage on its own terms if I got married again. I mean, I like the tradition. A friend of mine wrote a line, 'Without tradition, new things die.' And I don't want new things to die."
Theron also openly spoke of her love for her man, telling Esquire in April that she was "shocked" to have fallen for Penn. "I'm a very, very, very lucky girl," she told the mag. "Very lucky. He's hot."
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She told Elle UK, that Sean was "the love of my life."
"Putting aside that he's my partner, he's the love of my life," the mom to little Jackson, someone Sean wanted to adopt, told the publication. "For the first time, I felt that my work was really bleeding into my life and that made it hard."
Charlize even seemed to have the blessing of Sean's daughter, Dylan. "They're a great couple. They're both very happy and yeah, I love it," she said. "They're both extremely strong personalities and they're very intelligent so conversation lasts between them."