New York’s most-photographed landmark just became its hardest apartment to snag.

Nearly every unit publicly listed for sale at Manhattan’s famed Flatiron Building has already found a buyer, cementing the century-old triangular landmark as the most sought-after residential conversion in Manhattan just as it prepares to open its doors this fall.

Of the 22 residences StreetEasy has shown as listed for sale at 175 Fifth Ave., only four remain unsold, putting the building at roughly 82% absorption on its public listings. That kind of pace for a building still finishing construction has stunned brokers who track the city’s luxury new development pipeline, where units routinely sit for a year or more before finding takers.

The latest proof came last week, when the Flatiron Building notched its second straight appearance atop Olshan Realty’s weekly contract report.

Unit 17-North, a four-bedroom spanning 4,626 square feet with a 63 by 27-foot great room overlooking Madison Square Park, went into contract asking $23.95 million. Its final price, as well as its forthcoming owner, are not yet known until the deal closes.

It marks the second time in three weeks that a unit inside the building has claimed the No. 1 spot in the report, a rare feat for any single address. It’s also one that puts the successful conversion ahead of the ultra-exclusive new-construction towers it finds itself competing against for the city’s wealthiest buyers.

Few buildings anywhere carry the instant global recognition of the building’s razor-thin silhouette, a shape so famous it lent its name to the entire neighborhood surrounding it. Built in 1902 to a design by Daniel Burnham, the 22-story tower spent well over a century as commercial office space before Macmillan Publishing, its last major tenant, moved out in 2019 and left the building largely vacant.

What followed was a saga befitting the property’s outsized reputation. When the Flatiron Building’s owners couldn’t agree on its future, the property went to auction in 2023, where a little known bidder named Jacob Garlick won with a bid of $190 million and then vanished without ever putting down his deposit.

A second auction that spring produced a winning bid of $161 million from those existing owners, which then partnered with the Brodsky Organization to reimagine the office relic as residential real estate.

The developers tapped Studio Sofield to handle the interiors, a decision that has become central to the building’s marketing pitch. The firm reworked the awkward angles created by the building’s wedge-shaped floor plates into a layout of one north-facing and one south-facing unit per level, plus two sprawling full floor residences on the top two stories.

Pricing across the 36 sellable units ranges from just under $11 million for a three bedroom to $58.5 million for the penthouse spanning the 21st floor. But not all units have hit the market yet, a representative for Corcoran Sunshine Marketing Group told The Post.

Sales launched quietly last fall, publicly early this year, and momentum has only built since.

In March, a buyer signed for the seventh floor at an asking price of $30.5 million, a unit originally planned as two separate apartments before the developers combined them into a single 7,700-square-foot home with ceilings over 10 feet tall. That deal briefly stood as the priciest inked at the building, a record since eclipsed as contracts have piled up on higher floors.

Amenities inside include a 60-foot lap pool, a fitness center, a sauna, a cold plunge pool, a billiards room and a residents’ lounge with a kitchenette — all tucked into a structure that was never designed to house any of it.

Construction crews have spent recent months replacing roughly 1,000 windows to landmark preservation specifications and installing the building’s first-ever exterior lighting scheme, details that have required extensive sign off given the Flatiron’s protected status.

Residences are expected to be move-in ready this fall, with the building’s full amenity package, including the lap pool, slated to open in early 2027.