The mystery over Jeffrey Epstein’s millions may lie with the notorious conman father of his alleged sidekick Ghislaine Maxwell, according to a report.

Pedophile Epstein amassed a huge fortune with properties around the world, including his stunning Upper East Side mansion — yet no one has ever shown exactly how the shady moneyman made his millions.

Now an insider has provided lawyers sworn testimony saying Epstein was secretly bankrolled by his reputed ex’s dad, disgraced media baron Robert Maxwell, according to The Sun.

The UK newspaper owner had stolen hundreds of millions from his company’s pension funds before his mysterious death in 1991 when he was discovered floating in the Atlantic Ocean after being on his yacht The Lady Ghislaine, named after his daughter.

It was soon after her father’s death that Ghislaine fled to the Big Apple and became closely tied to Epstein, leading to her arrest earlier this year for allegedly procuring girls for him.

The possible financial ties between Epstein and Maxwell’s dad were allegedly disclosed by model scout Jean-Luc Brunel from chats almost 20 years ago, The Sun said.

“Jean-Luc was telling [acquaintances] how Ghislaine’s father Robert Maxwell was one of the reasons why Jeffrey Epstein had money,” one of the Frenchman’s former close associates told the UK paper.

“He said Maxwell had been one of Epstein’s early investment clients. I assumed that Maxwell had invested in Epstein, who then used that money to make his own,” the source claimed.

The allegation was passed onto US lawyers investigating Epstein’s crimes and those of his alleged co-conspirators, in the form of sworn testimony, The Sun said.

Convicted pedophile Epstein hanged himself in his Manhattan lockup last August while awaiting further serious sex charges. Maxwell has denied charges against her, and Brunel has also denied any connection to any sex crimes.