A landlord in leafy Park Slope says he’s been mired in a nearly decade-long nightmare with a squatter from hell who’s turned his life into “The ‘Twilight Zone.’’

Thomas Diana — who bought the eight-unit building at 319/321 Third St. in the trendy Brooklyn neighborhood in 1988 — told The Post on Monday that one tenant has been taking him to the cleaners since 2019 by not paying a cent on her $2,600-a-month apartment.

“Screwed is a polite way of putting it,” Diana said.

“I would never buy another building in this city. I’ve had enough of this. They gotta fix this. There’s no reason that owners should be going through this crap for years.”

The tenant, identified in court papers as Rebecca Carmel, maintains that the apartment is legally rent-stabilized but that Diana schemed to exempt it from those restrictions to hike the rent — and that she’s put her rent in an escrow account till the matter is settled.

But the landlord claims he has yet to be shown any proof of her escrow — and that she is now weaponizing housing regulations to get a free ride.

Diana said the beef began when he enlisted Carmel to move into the apartment to serve as a live-in caregiver for an ailing elderly tenant and a close friend, Linda Rogers.

The two women split the monthly rent, with Rogers paying $1,000 and Carmel chipping in $850, and later $950, court records show.

But things began to unravel when Rogers died in February 2016.

According to Diana, Carmel initially asked for time to find a new place, which he agreed to. But instead of eventually leaving, she remained and claimed she was only required to pay her $950 share of the rent under the earlier deal when Rogers was still alive.

The case ended up in court, and in 2017, a judge imposed an $831 monthly “use and occupancy” payment on Carmel while the dispute played out — money Diana claims she only made until 2019.

Diana argued that the building qualifies for an “owner or employee occupied” exemption from rent-stabilization regs because he lived there himself in the past and later employed Rogers briefly as building super before she became seriously ill.

Carmel countered, in part, that the claim is a ruse because Rogers was never physically able to perform the work.

The case has since been mired in the courts, with Diana claiming Carmel has dragged her feet over the dispute for years, frequently changing lawyers when she shows up in court and asking for delays.

He said he’s meanwhile going broke and estimates he’s lost between $275,000 to $325,000 in rent, not including legal fees.

“This court case has become a Twilight Zone Marathon,” Diana told Fox News Digital.

“It drained my daughter’s college fund. Now we’re borrowing money to pay for college while this just keeps dragging on.

“It gets pretty stressful,’’ he told the outlet. “People think eviction cases are like TV where it takes two weeks. In New York it can take years, and this one has turned into almost a decade.”

Carmel’s lawyer did not respond to a Post request for comment, and she did not answer the door at the Park Slope building.

But in a statement to Fox Digital, her lawyer, Casey Gilfoil of Brooklyn Legal Services, maintained her client is in the right.

“Mr. Diana’s distortion of the facts in this case is a sad attempt to harass our client out of her rent-stabilized apartment, and he will not be successful,” Gilfoil said.

She said Carmel has been putting money in escrow.

Gilfoil said a judge had ruled that Diana improperly took the apartment off the rent-stabilization rolls and said all that’s left to be decided are the legal rent and any damages that should be awarded.

In New York City, the Rent Guidelines Board sets limits on annual rent increases for rent-stabilized apartments, which typically vary between 1% and 5%, according to the board.

The Big Apple also has generous squatter’s rights that allow a tenant who has established legal residency for at least 30 days to have certain rights that can make it difficult to evict them.

Diana said he’s now stuck in limbo.

“I blame everybody,” he said. “The media people, they’ve made owners out to be the most evil bastards, evicting everybody on Christmas Eve, which is nonsense. They pretend you can evict somebody in a month. No, it’s two years plus, even on a simple case.

“And I blame the elected officials, because I’ve been hitting them like crazy, and they’re all: ‘Well, it’s in the courts.’ I said, ‘No! I don’t want you to call the judge. I want you to fix the law.”

City lawyer and onetime public-advocate candidate JC Polanco commiserated with Diana on X.

“I’ve represented small single-family landlords who haven’t collected rent in four years and are still expected to pay mortgages, taxes, insurance, repairs, maintenance, and violations,’’ he said.

“Not because they’re slumlords, quite the opposite.

“These small units represent their dreams and savings. The courts allow endless adjournments while some tenants game the system. The landlord is on the brink of bankruptcy and foreclosure on their own homes due to scrupulous, bad-faith tenants.

“The taxpayer funds the tenant’s lawyer. The system is badly out of balance,’’ Polanco wrote.