Angelina dumped Brad after private eye uncovered Marion Cotillard affair

Angelina Jolie has filed for divorce from Brad Pitt after learning he was cheating on her with his sexy co-star, a well-placed source told The Post on Tuesday.

“She hired a private eye because she felt that he was fooling around with her on the set, and it turns out, he was. And that was the final straw,’’ the source said.

Pitt, 52, had been rumored to have been cozying up to his “Allied’’ co-star Marion Cotillard, 40, for months during the pair’s filming of the World War II drama in London.

The PI discovered that Pitt was cheating on his wife of two years with Cotillard — while also partying like a single guy on a mission, the source said.

“The atmosphere [off-set] was full of hard drugs and Russian hookers, and Angie was told Brad got caught up in it,’’ the source said.

“He’s in the throes of some insane midlife crisis, and Angie is fed up.”

But a source close to Cotillard denied the Pitt affair rumors and insisted she is still with her long-term partner, French actor and director Guillaume Canet.

“They are still very much together. They have been a couple since 2007 and have one child but have never married,’’ the source said of Cotillard and Canet.

The source could not confirm French reports that Cotillard is pregnant with her second child with Canet.

Jolie’s manager, Geyer Kosinski, said Tuesday, “Angelina will always do what’s in the best interest to protect her children.

“She appreciates everyone’s understanding of their need for privacy at this time,’’ he told E! News.

Pitt added in a statement to People magazine, “I am very saddened by this, but what matters most now is the well-being of our kids.

“I kindly ask the press to give them the space they deserve during this challenging time.”

In addition to her husband’s alleged affair, Jolie, 41, was sick and tired of constantly sparring over their lifestyle, another source told The Post.

She has increasingly wanted to quit Hollywood in favor of devoting herself full-time to traveling the globe for her humanitarian work, while Pitt prefers Tinseltown and its parties, the source said.

Jolie spoke before the United Nations in Manhattan just this past Friday to ask them to help millions of Syrian refugees.

“The older she gets, the more serious she becomes, and she is sick of the Hollywood thing,’’ the second source said.

“He wants to make movies. She doesn’t. It’s a fundamental difference. It’s how you live your life.’’

Making matters worse, Pitt is closer to Jolie’s famous actor dad, Jon Voight, than she is, the source said.

“Jon’s a Hollywood guy, and she’s been estranged. Brad hangs out with her father more than she does,’’ the source said.

Another source told TMZ that Jolie believes that her hubby’s drinking and pot-smoking is affecting their kids.

Add to that his “anger problem,” and the mom of six said enough is enough, the source told the website.

Jolie filed for divorce Monday, citing “irreconcilable differences.”

She is seeking physical custody of the couple’s kids, TMZ said. She doesn’t want Pitt to have joint physical custody, just joint legal custody. He would get visitation, according to her filing.

Jolie is not seeking spousal support, the website said.

Brangelina’s French chateau, Miraval — where the couple married in August 2014 — has been quietly on the market for a few months, and locals were told they were selling it because they are breaking up, a source told The Post.

Jolie has hired top gun Laura Wasser as her lawyer.

The court documents list the couple’s date of separation as Sept. 15, 2016.

The couple have been together since 2004.

A rep for Cotillard did not immediately get back to The Post.

it was almost .... Gawd why i was almost the ftc