"The Irishman" premieres at the New York Film Festival next month, without intermission.

Martin Scorsese’s upcoming gangster film “The Irishman” has a runtime of 3 ½ hours, making it the filmmaker’s longest movie and the the longest mainstream American narrative movie in more than two decades.

It will play for audiences for the first time on Sept. 27, day one of the New York Film Festival, but with the unusually early screening time of 3 p.m., making the epic the festival’s “opening day” selection rather than “opening night.” A source confirms that it will run without intermission.

“The Irishman” will run 210 minutes; by comparison,”Wolf of Wall Street” was 180 minutes, “Casino” was 178, “Gangs of New York” 167 and “Goodfellas” 147. All of the films, except “Casino,” received nominations for best director and/or best picture.

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Based on Charles Brandt’s nonfiction book “I Heard You Paint Houses,” “The Irishman” stars Robert De Niro as Frank Sheeran, a World War II veteran who became a mob hitman and played a role in union boss Jimmy Hoffa’s disappearance. Al Pacino stars as the notorious mob-connected Teamsters president in his first Scorsese film. Joe Pesci also stars as mob boss Russell Bufalino.

The film, which spans decades, has already made headlines due to its use of VFX de-aging technology. The trailer, which dropped earlier this month, gave a peek at a younger-looking De Niro.

At 210 minutes, “The Irishman” isn’t quite as lengthy as Kenneth Branagh’s “Hamlet.” The 1996 Shakespeare adaptation runs an impressive 4 hours and 2 minutes.

Scorsese is likely still perfecting the film before its world premiere in exactly one month — the NYFF page for the movie notes that the runtime may change. If the director doesn’t cut any more, “The Irishman” will hold the distinction of running longer than “Godfather Part II” (3:20), “Exodus” (3:27) and “War and Peace” (3:28). (The epic “Ben Hur” is just slightly longer, at 3:32.)

Using old math, long movies have historically been risky for studios because they limit the number of theatrical showtimes. But this is a Netflix movie, and the streamer plays by its own rules.

Netflix is releasing the movie in select theaters Nov. 1 before making it available to stream Nov. 27 — a short theatrical window that has proven to be a point of contention between the streaming giant and exhibitors.

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