The Army issued a warning to its personnel about the possibility of crazed “incel” extremists carrying out mass shootings at upcoming screenings of “Joker,” according to a new report.

Marked “For official use only,” the Sept. 18 e-mail advised service members planning to watch the movie in theaters to “identify two escape routes” and to “run, hide, fight” in the event of a shooting, Gizmodo reported.

“Run if you can,” the message said. “If you’re stuck, hide (also known as ‘sheltering in place’), and stay quiet. If a shooter finds you, fight with whatever you can.”

On Tuesday, the Army confirmed to Gizmodo that it issued the warning in light of alarming social-media posts flagged by the FBI from the “incel” — or “involuntarily celibate” — community of alienated men who feel they have been shunned by society and can’t get dates.

The Army e-mail explained that incels “idolize the Joker character, the violent clown from the Batman series” — an angry loner who turns to violence after too much rejection.

They also like “his depiction as a man who must pretend to be happy but eventually fights back against bullies,” the Army said.

An Army spokesperson said the message was routine.

“We want our workforce to be prepared and diligent on personal safety both inside the workplace and out,” the rep said.

In another memo on Monday, top officials of the Army’s Criminal Investigation Division said it received “credible” intelligence from law enforcement in Texas about “disturbing and very specific chatter” on the dark Web regarding “the targeting of an unknown movie theater during the release.”

“Joker,” starring Joaquin Phoenix in the title role, opens to the public on Oct. 4 — and has already sparked concerns of movie-theater violence.

The studio behind the flick, Warner Bros., is standing behind the movie, saying in a statement earlier this week that it “does not endorse real-world violence.”

Director Todd Phillips complained that countless other violent Hollywood movies, such as the “John Wick” franchise, weren’t given the same scrutiny.

“The movie still takes place in a fictional world,” he said.

“It can have real-world implications, opinions, but it’s a fictional character in a fictional world that’s been around for 80 years.”

“The one that bugs me more is the toxic white male thing when you go, ‘Oh, I just saw “John Wick 3.” ’ He’s a white male who kills 300 people and everybody’s laughing and hooting and hollering. Why does this movie get held to different standards? It honestly doesn’t make sense to me.”