A fourth woman has filed a lawsuit accusing former Soros Fund portfolio manager Howard Rubin of brutalizing her in his Manhattan penthouse sex dungeon, saying he ignored her repeated use of their agreed-upon safe word, “pineapples,” during an S&M session.

The woman, who has requested anonymity in her $7 million Manhattan Supreme Court suit as a rape victim, met Rubin through a friend in November 2015.

The pal set up a date between the then-60-year-old Rubin and the 20-year-old woman at the Russian Tea Room in Manhattan, the suit says. The woman was told she’d be paid $2,000 for dinner and drinks, but that she would not be required to have sex.

Rubin plied the young escort with pricey glasses of Don Julio 1942 Anejo tequila and then presented her with a nondisclosure agreement that said she could be sued for up to $1 million if she disclosed their relationship, according to court papers.

Rubin — whose high-stakes investing for billionaire George Soros was featured in the best-selling books “Liar’s Poker” and “The Big Short” — then invited the woman to his apartment at the luxury Metropolitan Tower.

At the penthouse pad, the married Rubin allegedly served his mistress a drugged drink and ushered her into his “dungeon-like ‘toy room,'” a 300-square-foot space with “ropes and toys to tie people up with, and electrocuting devices, and other devices,” the suit says.

She allowed Rubin to tie her wrists after he “explained that he would go easy on her, and that she had a safe word: pineapples,” the suit says.

“Rubin instructed plaintiff to say pineapples if she got uncomfortable, or if anything became too much for her,” the suit says.

But the financier ignored the woman after she shouted “pineapples” when he smacked her hard across the face, the suit says. She begged him to stop as she repeated the safe word while he beat and raped her, first anally with a “big black dildo” and then vaginally with his penis, the suit says.

“When Rubin concluded, he told [her] that she was a ‘whore’ and to ‘clean’ herself up,” the suit says.

He then kicked her out of his apartment, saying he had to meet his wife and kids for dinner, according to court papers.

The friend who introduced her to Rubin warned her not to go to the police because Rubin “was extremely wealthy and powerful, and would destroy her life,” the suit says.

She finally decided to sue after a suicide attempt.

Edward McDonald, attorney for Rubin, said his client “categorically denies all the allegations of misconduct.”

“This is another unfounded attempt to obtain money from Mr. Rubin,” McDonald said.

Three other women sued Rubin in Brooklyn federal court last year, making similar claims. That case is still pending and Rubin declined to discuss the allegations.