A retired NYPD sergeant has vowed never to relinquish any part of his pension to his ex-wife — even though he’s under court order to do so.

“I will never break. . . If my lungs move, she will never get my pension,” Sebastian Giangregorio wrote in an e-mail shortly before his 18-year marriage to wife Lisa ended in Florida.

In a Facebook post shortly before he retired, he wrote, “I’m a fighter … If I have to work 20 more years, she will not get my pension.”

According to his ex-wife, the former cop, 45, has since moved back to The Bronx, traveled around the world, and ignored an Oct. 24, 2015, court order to pay half his $5,540 monthly NYPD pension and mortgage payments on the house where she and their three children, ages 7, 19, and 20, live.

The house is going into foreclosure, Lisa Giangregorio told The Post.

“There’s no reason why my kids and I should face being thrown into the street. I can’t afford to keep battling to get what’s rightfully mine.”

While Lisa struggles, Sebastian recently vacationed in Aruba with a 24-year-old Venezuelan woman, who chatted with Lisa on Facebook.

“I am in love, I love everything about him,” the woman told the ex-wife, adding, “He gives me money.”

After Lisa informed her that Sebastian “has three children he doesn’t see,” the woman claimed they had a son together.

Despite Lisa’s pleas, the New York City Police Pension Fund says its hands are tied.

Last month, a Florida judge signed an order requiring the pension fund to pay Lisa directly.

But a lawyer for the fund, Nicole Giambarrese, said it cannot legally do so because the ex-cop has failed to sign a consent form to have the Florida order recognized in New York. If he doesn’t sign it, his ex-wife must go to court in New York to make the order effective in the Empire State.

That would cost thousands in legal fees, and Lisa would have to serve her ex-husband to give him a chance to contest the order before a judge approves it.

“Pension funds can be very complicated, and there’s often a lot of red tape involved in securing payouts for the spouse,” said Karen Winner, a matrimonial lawyer who teaches divorce-related financial fraud at John Jay College of Criminal Justice.

“I’ve seen so many women lose their pension entitlements in divorce. It’s an expensive process to enforce one’s rights in this system, and it can drag on for years.

Lisa and their kids moved from Westchester County to Naples, Fla, in 2014. Sebastian joined them in 2015, while collecting unused vacation pay, she said. He retired from the NYPD in February 2016 after 22 years on the force. He had pumped up his pension by working a lot of overtime his last three years — making $141,747 in 2014-15, records show.

During the couple’s rocky break-up, amid accusations of domestic violence, the Collier County Sheriff’s Office arrested Sebastian on charges of stalking Lisa and threatening to “get a gun” and kill her.

But a judge dismissed the charges after refusing to admit cell-phone evidence that Sebastian had violated an order of protection. The matrimonial judge, in ordering the pension payments, found Lisa barely making ends meet on her hair-stylist salary, while Sebastian “lives an extravagant lifestyle and has family funds readily available to him.”

The ex-cop did not return messages left on his cellphone.