O.J. SIMPSON is stabbing his ex-lover Kris Jenner in the back by siding with her estranged hus­band Bruce in their $175 million divorce battle – and he’s offering to reveal explosive evidence that can de­stroy Kris’ character, say sources.

The disgraced gridiron great – who had an affair with Kris in the mid-1980s when she was married to O.J.’s best buddy Robert Kardashian – reached out to Bruce from behind bars, telling him he has a secret stash of material that can be used against the Kardashian matriarch.

The 66-year-old convict also claims he has proof beyond a shadow of a doubt that he is the REAL father of Kris’ daughter Khloe.

“O.J. told Bruce, ‘I’ll help you destroy Kris!’” revealed an insider.

Simpson despises the tough-as-nails clan “momager” because she wrote in her 2011 book, “Kris Jenner…and All Things Kar­dashian” that she “instinctively knew that in some way O.J. had something to do” with the murder of his ex-wife Nicole. O.J. was famously acquitted of that crime in 1995.

“Simpson has hated Kris ever since she portrayed him as a brutal monster in her book,” said an insider. “He’s vowed to get even with her someday and says helping Bruce in the divorce is a golden opportunity.”

O.J. is also said to be infuriated that Kris keeps insisting he’s NOT Khloe’s father and has turned her daughter against him.

Simpson is serving a nine- to 33-year sen­tence in the Lovelock Correctional Center in Nevada for a 2008 conviction on armed robbery and kidnapping charges. He isn’t eligible for parole until 2017, although a Las Vegas judge is reviewing whether he should get a new trial.

“O.J. wrote Bruce a letter when he heard about his split from Kris,” divulged an in­sider. “He said he could help Bruce win millions from her.”

He invited Bruce to either visit him in prison or call him to learn all the shocking details about the dirt he has on Kris, said the source. For now, O.J. is keep­ing the most damaging evidence to himself, saying only that it is stashed away in one of the half-dozen or so storage lockers he has under pals’ names in Califor­nia and Florida.

But he is revealing that he has definitive proof that Khloe, 29, is his daughter.

“O.J. resents how Kris denied it and acted like he’s a delusional fool,” said an insider. “She handled his claim as if it was a joke, and that re­ally upset him. Now he’s out for blood.”

Sources say Khloe grew up doubting whether attorney Robert Kardashian was her bio­logical dad, and Robert himself once questioned it because Kris was sleeping around at the time.

“Khloe reached out to O.J., and he told her point-blank that he is her father and that he loves her,” said the insider. “That’s when Kris laughed it off and told Khloe to forget about him. But now, O.J. says he’s got a letter Kris wrote back in the 1980s, and in it she admits that Khloe is his child. To O.J., it is the final proof about Khloe, and he wants Bruce to use it in the divorce case, too.”

Ironically, O.J. remained a close friend of Kris’ even after she married Bruce, and their families vacationed together in the Mexican resort of Cabo San Lucas during the Easter holiday in 1994, just three months before Nicole was murdered.

But now, O.J. will apparently stop at nothing to reap vengeance on Kris. Along with the damning evidence, he’s also offering to testify in the divorce proceedings.

Said the source: “O.J. is sure he can personally rip apart Kris’ character.”