The longtime home of Vartan Gregorian, the man who was known to have saved the New York Public Library from decay, has hit the market for $4.35 million, The Post has learned.

Gregorian, who was an Armenian immigrant, passed away last April after being hospitalized for stomach pain. He was 87.

A philanthropist and academic scholar, he is widely credited for saving a down-on-its heels New York Public Library (NYPL) system in the 1980s.

Gregorian had taken over as president during that time and used his charm to fund the library, branch buildings and services throughout the Bronx, Staten Island and Manhattan that had deteriorated after a decade of budget cuts.

The disrepair was then symbolized by the dirt that streaked the iconic marble lions, Patience and Fortitude, who still guard the Fifth Avenue entrance to the Beaux-Arts main library today.

During Gregorian’s tenure as president of the NYPL from 1981 to 1989, the library’s Main Branch in Manhattan was restored with $42 million. He was also successful in getting approval from city planning authorities to restore the nearby Bryant Park.

Spanning 2,600 square feet, Gregorian’s condo of nearly 25 years, near Columbus Circle, is made up of three bedrooms, and three bathrooms. Situated on the 18th floor, it was first purchased by the educator and historian in 1997 for $3.2 million, records show.

“It’s taken a quarter of a century for this standout apartment in one of New York’s most iconic buildings to come to market,” the listing notes.

Upon entrance is the foyer lined with bookshelves. Features include two primary bedrooms, each with an en-suite bathroom. There is also a third bedroom that can be used as an office.

The formal living room features a wood-burning fireplace.

Built in 1931, the pre-war building at 340 West 57th St., known as Parc Vendome, boasts easy access to Columbus Circle, Carnegie Hall, Broadway and Lincoln Center. Amenities include full-time doormen, award-winning formal gardens, a billiards room, music room, library, private dining room and card room, the listing adds.

“Offered by the estate of Vartan Gregorian, the world renowned philanthropic foundation and university leader, historian, and humanist, this residence hits every note on your wishlist,” the listing states.

Lisa Tarnopol Deslauriers and Linda Reiner of Coldwell Banker Warburg hold the listing.

Gregorian, born to Armenian parents in Tabriz, Iran, had arrived in America in 1956 to study history and the humanities at Stanford University.

“As President from 1981–89, his leadership and tenacity revitalized and reaffirmed the Library as the preeminent civic and educational institution that New Yorkers know and love today,” the NYPL said in a statement.

“Through his efforts and leadership, the Library was able to weather, recover, and rebound from a decade of fiscal crisis, restoring hours of service in the branches, renovating many historic locations, growing and strengthening circulating collections with a focus on multilingual and multicultural materials, increasing education and literacy programs, and investing in curators and expert staff in the research libraries, among other things.”