When Harper Lee died in 2016, the rent on her stabilized Manhattan apartment was $845.89 per month.

The acclaimed author of “To Kill a Mockingbird” split her time between Yorkville and her hometown, Monroeville, in southern Alabama. Though she didn’t occupy her ground-floor one-bedroom after suffering a stroke in 2007, she held onto the lease for nine more years, until her death at age 89.

The apartment was warehoused until last year — when it was rented to its current tenants for $2,950, according to a lawsuit filed this week by the couple currently living there.

After the lease expired — last May 31, coincidentally the same day Con Ed found a gas leak and shut off gas to the building — the tenants had their rent reduced to $2,450 “by mutual agreement” due to the lack of cooking gas, according to court papers. The gas dryers in the basement laundry room are also out of service.

“The apartment was rented to the Pulitzer-prize winning author Harper Lee from 1967 until her death in 2016,” the lawsuit says. “Thereafter the apartment was kept vacant until it was rented to plaintiffs in 2022.”

The court complaint says that “it was illegal to deregulate the apartment,” and the rent should therefore be rolled back to $845.89 — with the tenants also entitled to treble damages for the overcharges, plus interest and legal fees.

The apartment’s rent history shows that, in 1984 — when the law began requiring landlords to register stabilized rents with the state’s Division of Housing and Community Renewal — Lee paid $291.74 per month. (In today’s dollars, that equals $879.02.)

Several neighbors told The Post that the apartment was renovated at some point after Lee’s death, but couldn’t remember when.

The historic, albeit nondescript, apartment is in the back of a 1950 brick building, facing a courtyard with trees. It was originally listed on StreetEasy last year for $3,150 a month.

When the 1-year lease for the current tenants expired, it was not renewed, though the tenants continued to pay rent, the lawsuit says.

“We don’t know yet why they weren’t offered a renewal lease,” said their lawyer, Ronald Languedoc of Himmelstein McConnell Gribben & Joseph.

Lee arrived in New York in 1949 and worked as an airline reservation agent. She lived in a cold-water flat on far East 82nd Street until around 1967, when her building was razed to make room for a 20-story rental tower, so she moved across the street.

Lee had no spouse or children, and kept her affairs private. She went by her first name, Nelle, pronounced “Nell.” One neighbor said that her apartment, around 600 square feet, was “jam-packed and piled with stuff.”

During Lee’s years of absence from New York, she remained up-to-date on her rent, the live-in property manager, Steve Austern, told The Post shortly after her death in 2016. He did not respond to requests for comment. The current tenants also declined to comment, as did Donald Sheffey, the real-estate agent who listed the apartment last year.

“To Kill a Mockingbird,” which dealt with racial issues in the Deep South, was published in 1960 and won the Pulitzer Prize the following year. Controversy ensued decades later over the posthumous publication of Lee’s second novel, “Go Set a Watchman,” which portrayed Atticus Finch with different racial views.