The latest Marvel superhero flick set the record at around noon, Walt Disney Company Korea said based on a real-time box-office tally from the Korean Film Council.
The previous No. 1 was "Avatar" (2009), which sold 13.30 million tickets from 2009 to 2010.
"Endgame," the epic finale to the superhero studio's decadelong series, has been breaking South Korea's box-office records since its release on April 24.
It has since claimed the biggest single day and opening day record with 1.3 million admissions while selling the most tickets in the first week.
On the 11th day of its run, the movie passed the 10 million mark, becoming the 24th film and the third Marvel film ever to hit the milestone. The movie surpassed 13 million on the 22nd day.
A film seen by an audience of 10 million is considered a huge success in a country with a 51.7 million population.
In "Endgame," the Avengers' surviving superheroes, who became Earth's last hope after the end of "Avengers: Infinity War," battle the villain Thanos. (Yonhap)