It’s the door that launched a thousand spats.

A Chinese passenger aboard the sinking Titanic survived the horror by clinging to a floating door in the icy Atlantic – inspiring one of the blockbuster film’s most iconic and debated scenes, his grandson revealed.

Fang Lang miraculously survived when the doomed ocean liner went down in April 1912, an ordeal later depicted in James Cameron’s 1997 epic “Titanic,” which shows Kate Winslet’s Rose DeWitt Bukater taking refuge on a wooden door after the infamous sinking.

“With my grandfather’s story, he actually went down with the ship, and to everyone’s amazement, he found his way onto a door,” Steven Fong told CBS New York this week.

“In the theatrical movie, James Cameron does reveal that my grandfather inspired the Jack and Rose ending scene,” he said, referring to the 2020 documentary “The Six,” which the Oscar-winning director helped develop with author Steven Schwankert. 

Lang’s harrowing tale – echoed in the legendary film’s ending – has sparked years of heated debate among moviegoers over whether Leonardo DiCaprio’s character, Jack Dawson, could have made it onto the floating panel with Winslet’s character after the ship sunk. 

In the movie, Rose makes it onto the door while Jack remains in the frigid water and eventually dies before she’s rescued by the RMS Carpathia. Angered fans believe Jack’s death was unnecessary.

But Cameron has insisted that “only one could survive.”

Lang was one of eight Chinese passengers aboard the Titanic’s ill-fated maiden transatlantic voyage.

Only six survived after the ship struck an iceberg and sank on April 15, 1912, killing about 1,500 passengers who drowned in the freezing North Atlantic. 

“Fang Lang was plucked from the water, one of only four passengers rescued from the water,” Schwankert said. 

He was pulled aboard the Carpathia, later made his way back to America, opened a bakery, and had two sons – though Fong said his grandfather never discussed the Titanic with his family. 

The extraordinary story of the six Chinese survivors will take center stage in “The Unsinkable,” a production opening next year at New York City’s Perelman Performing Arts Center. 

“It’s such a surreal feeling, you know, being part of, like, this legacy, this big story that everybody knows about,” Fong told the outlet. 

“We’re just so humbled by the opportunity to kind of add that to the story.”